Marciello debuted in karting in 2005 and raced in various European championships, working his way up from the junior ranks to progress through to the KF2 category by 2010.
In 2012 Marciello continued his collaboration with Prema Powerteam into Formula 3 Euro Series.[6] and the revived FIA European Formula Three Championship. In FIA F3 he finished 2nd in the championship, with nine podiums including seven wins. In Euro Series he finished 3rd with ten podiums and six wins. In both championships he scored more wins than anybody else.
He remained in F3 for 2013, and emerged as a pre-season favourite following his impressive results in the previous year and dominant performances in pre-season testing.[7]
Toyota Racing Series
During the 2012 off-season Marciello competed in New Zealand-based Toyota Racing Series, taking ninth place in the championship with a win at Hampton Downs.[8]
On 20 January 2014, the Ferrari Driver Academy announced Marciello would be racing in GP2 in 2014. However, they did not confirm the team he would be competing with.[10] On 18 February, it was announced he would be driving for the Racing Engineering team.[11]
Marciello achieved his first GP2 victory in the feature race at Spa-Francorchamps after an intense fight with McLaren junior driver Stoffel Vandoorne in the closing stages.
He joined Trident Racing for 2015,[12] but struggled to capitalize on his 2015 debut, finishing seventh overall.
On 31 December 2014 it was announced that Marciello had signed as test and reserve driver for the Sauber Formula One team for 2015.[14][15] In January 2016, it was announced that Marciello had been dropped by Sauber[16] and had split with the Ferrari Driver Academy for personal reasons.[17]
Ahead of the 2018 season, Mercedes-AMG added Marciello to their rank of Performance drivers, thus making him a fully-fledged factory driver.[22] The season saw him returning to both the Endurance Cup and Sprint Cup series where, once again with AKKA ASP, he paired up with Meadows in the latter and drove alongside Tristan Vautier and Daniel Juncadella in the former.[23] Marciello performed to a high level, taking second-placed finishes in the Endurance rounds at Silverstone and - after initially being awarded victory when a suspected technical non-compliance for the winning team caused them to be provisionally disqualified - Barcelona, which led him to a runner-up spot in the Endurance Cup.[24] Having inherited the title at first, an appeal by the disqualified team stripped the accolade from Marciello, with the disqualification being converted into a fine.[25] Meanwhile, wins at Budapest and the season finale at the Nürburgring alongside a slew of further podiums gave Marciello and Meadows the Sprint Cup title.[26][27]
That year, Marciello also partook in all four rounds of the Intercontinental GT Challenge with Mercedes. He scored podiums at Bathurst and Spa, as well as taking a win at the Suzuka 10 Hours, the latter earning him the provisional championship lead, though a seventh place at Laguna Seca, a race in which Marciello damaged his car and received a drive-through penalty after a mistimed move on the WRT Audi of Sheldon van der Linde, set him back to third in the standings.[28][29][30]
2019: Maiden Macau crown
Continuing into a third season of the Endurance and Sprint series at AKKA ASP, Marciello would be partnered by Vincent Abril in both championships, with the pair being joined by Michael Meadows for the endurance rounds.[31] In the Sprint Cup, Marciello was unable to defend his title, even if a win at Zandvoort and a pair of victories at the season finale in Hungary earned him and Abril third in the championship, one the pair battled for until the final race of the season.[32] As well as this, the final victory at the Hungaroring guaranteed AKKA ASP the teams' title.[33] Their campaign in the Endurance Cup proved less fortunate, as retirements in two races saw the Italian end up 25th overall.
Marciello took part in the FIA GT World Cup, held at the prestigious Guia Circuit in Macau, at the end of the year with Team GruppeM. Having taken pole position for the event the previous year, the Italian repeated said feat in 2019, before proceeding to control Saturday's qualification race and winning the main race, therefore becoming the GT World Cup winner for the first time.[34][35][36]
2020: ADAC GT Masters debut
Despite a truncated year due to the outbreak of the COVID-19 pandemic, Mercedes would expand Marciello's full-time racing duties, with him not only driving for AKKA in the rebranded GT World Challenge Europe Endurance and Sprint cups, but also taking part in the ADAC GT Masters alongside Philip Ellis.[37][38] That campaign proved to be largely anonymous, say for the final race at Oschersleben, where Marciello and Ellis took victory from pole position.[39]
His campaign in the Endurance Cup would see more success than the previous year: partnering Felipe Fraga and silver-ranked Timur Boguslavskiy, Marciello and his team ended up fifth in the standings, having taken a pair of podiums at the start of the year before encountering brake issues at the 24 Hours of Spa which ended their championship challenge.[40] In the Sprint Cup, Marciello helped Boguslavskiy towards wins at Misano and Barcelona, though he would finish third in the drivers' standings - one place behind the Russian, who himself ended up mere four points behind the title-winning duo of Dries Vanthoor and Charles Weerts - as he missed the round at Zandvoort due to his commitments at the 24 Hours of Nürburgring.[41][42][43]
2021: Further victories in GTM and GTWC
Marciello remained in the ADAC GT Masters for 2021, this time driving at Mann-Filter Team Landgraf-HTP WWR together with Maximilian Buhk.[44] The season began promisingly, as the duo converted pole to victory at the season opener in Oschersleben in a commanding performance.[45] The team would score two further podiums during the first eight races of the season, which was enough to close the gap to just three points compared to the leading Land-Motorsport outfit of Ricardo Feller and Christopher Mies.[46] However, a retirement at the Sachsenring owing to a crash caused by Albert Costa and a 30-second penalty which led to a finish outside of the points in Hockenheim put the title out of reach for Marciello and Buhk, who ended the season fourth overall.[47][48]
The Italian also drove for the AKKA ASP Team in the SRO competitions, being joined by new Mercedes factory driver Jules Gounon on a full-time basis in the Endurance Cup and once again partnering Timur Boguslavskiy in the Sprint Cup.[49][50] In the former series, Marciello and Gounon were able to mount a title charge, taking second places at Monza, a race which Marciello led during the opening stint, and at the Nürburgring, where the team ran in second for the majority of the contest.[51][52] Additionally, Marciello scored a second successive pole position for the 24 Hours of Spa, though the team would retire due to damper failure.[53][54] The points they lost in Belgium cost the outfit during the final round in Barcelona, where, despite taking victory alongside Felipe Fraga, Marciello and Gounon would miss out on the championship by four points.[55] In the Sprint Cup, Marciello and Boguslavskiy scored four podiums but failed to win a race, leading to a third-placed finish in the drivers' standings.
Near the end of the year, Marciello confirmed that he would be switching to a Swiss racing licence from 2022 onwards, citing a lack of support from the governing body of Italian motorsport as the reason for his "overdue" switch.[56]
2022: GTM and Endurance Cup titles
Team Landgraf and Marciello were reunited for the 2022 ADAC GT Masters season, with a variety of teammates accompanying the Italian across the season.[57] A double podium to start the year off was swiftly followed by Marciello's first pole at the Red Bull Ring, one which he converted to third place in the race. Following that round, teammate Jonathan Aberdein was replaced by Lorenzo Ferrari, with personal issues between Marciello and the South African and a lack of pace from the latter being the speculated reasons for said decision.[58][59] A disappointing event in Zandvoort was the result, though Marciello would bounce back at the Nürburgring, winning the opening race and finishing second on Sunday alongside fellow factory driver Maro Engel and taking the championship lead in the process.[60][61] The Swiss driver was joined by Daniel Juncadella, another factory driver of the German brand, for the remaining three rounds, where he took three further podiums as well as two pole positions, which enabled him to clinch the title one race early at the Hockenheimring.[62]
In addition, another double campaign at AKKodis ASP in the Endurance and Sprint cups was in store for Marciello.[63][64] Once again, he was joined by Boguslavskiy in the Sprint Cup, where wins at Brands Hatch, Magny-Cours and Zandvoort, along with a heap of fastest laps and pole positions on Marciello's part, enabled the pair to fight for the title, though they would lose out for a third successive year to the WRT duo of Vanthoor and Weerts. Despite this, Marciello managed to clinch the overall GT World Challenge Europe title at the final Sprint Cup round.[65] This was compounded by a notable season in the Endurance Cup: having earned top honours at the 24 Hours of Spa, the trio of Marciello, Jules Gounon and Daniel Juncadella ended up winning the championship at the season finale in Barcelona, beating Ferrari's Antonio Fuoco by two points.[66][67]
Marciello's main campaigns would, once more, lie in the European SRO competitions, as he remained with Boguslavskiy in the Sprint Cup and joined him and Gounon for a title defence in the Endurance Cup.[70][71] The Endurance Cup season opener at Monza ended with retirement, with Boguslavskiy causing race-ending damage with a misjudged defensive move, though the team bounced back with a victory at Le Castellet, where Marciello charged through the field during the final hours to take victory.[72][73][74] A second place at the 24 Hours of Spa was followed by a win from pole position at the Nürburgring.[75][76][77] The gap the team had amassed meant that a fifth-placed finish at Barcelona was enough to clinch back-to-back titles for Marciello and Gounon.[78][79][80]
The Swiss driver was able to stamp his mark on the Sprint Cup campaign as well, which started with a victory apiece at Brands Hatch and Misano, with dominant opening stints from Marciello being the catalysts for success.[81][82] The duo retired during the first race at Hockenheim, but would bounce back to win on Sunday in spite of gear-shifting issues which manifested during Boguslavskiy's stint.[83] Another pole position truncated by an imposing first stint from Marciello earned AKKodis victory in Valencia, though this would not be enough to take home the Sprint Cup title, with a collision caused by Audi's Lorenzo Patrese ending the team's final race at Zandvoort, therefore crowning the Tresor Orange1 outfit as champions.[84][85]
Parallel to his GTWC commitments, Marciello partnered John Ferguson in the British GT Championship.[86] With a win at Snetterton, Marciello and Ferguson helped Ram Racing to fourth place in the teams' standings.
In November 2023, Marciello would drive his final race as a Mercedes-AMG factory driver, competing at the FIA GT World Cup in Macau with Team Landgraf.[87] A dominant weekend followed, as Marciello took pole, won the qualifying race on Saturday and clinched world cup honours with a faultless drive on Sunday.[88][89][90] With his departure imminent, Marciello presented his Macau victory as a "last gift" to the Mercedes brand he had been a part of for the previous seven years.[91]
† As Marciello was a guest driver, he was ineligible to score points. ‡ Points only counted towards the Michelin Endurance Cup, and not the overall LMP2 Championship. * Season still in progress.