Lucas started karting in 1998, taking his first big placing in 2001 when he karted in the Formula A World Championship and finished second. He also took third om the 2001 ICC Panamerican Sudam Championship. He graduated to the Formula Renault 2.0 Brazil in 2002 with G Force Motorsport where he took 6 podiums out of 10 races, with 2 being wins, and placed as runner up in his rookie year. From there, di Grassi joined Avallone Motorsport in 2003 for the Formula 3 Sudamericana series where out of the 12 races, he took 11 podiums with one of them being a win. His track record left him second in the standings. Lucas also joined Prema Powerteam for the Formula 3 Euro Series where he raced for four races and finished 21st in the standings.
2004 was a much busier year for di Grassi. He joined Hitech Racing for five different series. He raced full time in the British Formula 3 Championship where he took 4 podiums and 2 wins to finish 8th in the standings. He then entered the Bahrain Super Prix where he finished 19th, the Macau Grand Prix where he finished 3rd, Masters of Formula 3 where he finished 5th and FIA European Formula Three Cup where he finished 6th. He returned back to the Formula 3 Euro Series in 2005 with Manor Motorsport where he took 5 podiums and a single win to place 3rd in the standings. Lucas also competed with the team for the Macau Grand Prix where he won the race and the Masters of Formula 3 where he finished 3rd.
He went on to graduate to the GP2 Series in 2006 where he joined Durango for his rookie year. He managed to take 8 points and placed 17th in the standings. He remained in the championship for 2007 where he made the move to ART Grand Prix. His second year was an improvement as he went on to take 6 podiums and a single win to finish as runner up in the standings. Lucas came back for a third year in 2008 with Barwa International Campos Team where he took 3 wins and 2 more podiums and placed third in the champions. In his fourth and final year of his GP2 Series, he joined Racing Engineering where he took 8 podiums, of which one was a win, and finished 3rd in the standings.
2012 was the year he debuted in endurance racing where he joined Audi Sport Team Joest for the FIA World Endurance Championship. He raced in a single race where he took a single podium and placed himself 22nd in the standings. Alongside this, Lucas raced with AF Corse in the City of Dreams Macau GT Cup where he finished 17th. He also raced with Tekno Autosports in the International V8 Supercars Championship and with Dörr Motorsport in the 24 Hours of Nürburgring. He returned with Audi Sport Team Joest in 2013 for three different series. He completed 2 races in the FIA World Endurance Championship where he took a podium in each race to finish ninth, the 24 Hours of Le Mans where he finished third and the American Le Mans Series. Di Grassi stuck with both the FIA World Endurance and the 24 Hours of Le Mans in 2014 with the team, where he took 4th in the championship and 2nd in Le Mans. He also raced with Ipiranga-RCM in the Stock Car Brasil.
He continued with the FIA World Endurance Championship championship from 2015 and 2016 where he took fourth and second, taking 5 podiums and 2 wins across the two. He also competed in the 24 Hours of Le Mans in both years where he took fourth and third. Lucas competed as a guest in the Stock Car Brazil once again in both years.
Di Grassi debuted in the Audi Sport TT Cup with Audi Sport in 2016 where he won with five podiums and two race wins. From there, he moved to the FIA GT World Cup in 2017 with HCB-Rutronik-Racing but he didn’t manage to finish the race. He returned back to Stock Car Brazil in 2018 with HERO Motorsport where he took three wins and 12th in the standings. In that same year, he raced his first WeatherTech SportsCar Championship with Mazda Team Joest where he finished 46th. Lucas headed back to Stock Car Brazil with Eurofarma RC for 2019 where he proceeded to finish 34th.
Lucas made his debut in Formula One in 2005 where he joined Mild Seven Renault F1 Team as a test driver. The team proceeded to make a name change to ING Renault F1 Team in 2007 where di Grassi made his return as a test driver after a year out. He continued as a test driver for the team in both 2008 and 2009. Alongside Renault, he became a test driver for Honda Racing F1 Team in 2008. In 2010, di Grassi joined Virgin Racing for his first and only full season in Formula One. He didn’t manage to take any points and finished 24th. He then headed to Pirelli as a test driver for 2011.
Di Grassi debuted in the FIA Formula E with Audi Sport ABT in 2014 to 2015. In his rookie year, he took six podiums where one was a win to finish 3rd in the standings. He stuck with the team for a second year when they made the name change to ABT Schaeffler Audi Sport where he took 4 podiums and 3 wins to finish second in the standings. Lucas stuck with the team for the 2016 to 2017 season where after a further 5 podiums and 2 wins to take the championship title.
The team made the name change to Audi Sport ABT Schaeffler in 2017 to 2018 where di Grassi joined them for a fourth year. He took seven podiums in total, of which 2 were wins, and he placed himself second in the standings. Lucas remained with the team for the 2018 to 2019 season where he finished 3rd with 2 wins and a further 1 podium.