After competing in karting, Thiim won the 2006 Danish Formula Ford Championship. In 2007 he switched to touring car racing, where he finished 5th in the Seat León Supercopa Germany and raced a BMW 3 Series in the Danish Touring Car Championship.[2] The driver won the 2008 Seat León Supercopa Germany with 8 wins in 16 races.
In 2012, Thiim raced in the Porsche Supercup and Porsche Carrera Cup Germany, finishing 3rd in both. He also got three podiums in the ADAC GT Masters driving a Porsche 911. He continued in both the Porsche Supercup and Porsche Carrera Cup Germany in 2013 and became Porsche Supercup champion.[4] In the same year, he scored the overall victory at 24 Hours of Nurburgring
Thiim is a popular driver in the Sim racing scene racing mainly on the iRacing service. He frequently uploads his races on his Twitch and YouTube channels.[7] He often refers to his fanbase as "TeamThiim" and has over 20,000 YouTube followers. As well as frequently streaming his races on Twitch.tv.
Nicki Thiim is also well known for his charity 12 hour race where he raised money for Danish children with cancer by hosting a sim racing event attracting over 45 teams and 200+ drivers and raised over 100,000 DKK.
Nicki is also a huge fan of the Ford Ka, which he believes is a compact yet substantial car to drive.