In the 2009 off-season, Germain signed his first professional contract agreeing to a three-year deal. He had previously played in the Monaco Championnat de France Amateur (CFA) team that won the reserve team title in the 2008–09 season.[5] Despite signing professional terms, the striker spent the next two seasons playing in the club's reserve team. Germain made his professional debut on 1 May 2011 in a league match against Saint-Étienne appearing as a substitute.[6] He played in the team's final league match of the season against Lyon appearing as a substitute in a 2–0 defeat.[7] The defeat confirmed Monaco's relegation to Ligue 2.[citation needed]
In the second division, Germain was permanently promoted to the senior team and, on 15 August 2011, he scored his first goal for the club in a 2–1 loss against Reims.[8] In the following month, he scored his second career goal in a 2–2 draw against Sedan.[9] In the 2012–13 campaign, Germain scored 14 goals in 35 matches for AS Monaco as they got promoted to Ligue 1. On 23 July 2013, Germain signed a contract extension with Monaco, keeping him at the club until 2017.[10] Germain was part of the AS Monaco side that won the 2016–2017 Ligue 1 title, contributing with 10 goals.[11]
In July 2015, Germain joined Nice on loan from Monaco. Nice had an option to buy him after the end of the loan spell.[12]
Following his departure from Marseille in the summer of 2021, Germain remained on the south coast of France, signing for fellow Ligue 1 side Montpellier.
Macarthur FC
After his 2 year contract with Montpellier expired, Germain moved to Australia to sign for Sydney based A-League club Macarthur FC, signing a two-year deal.[15]
He made his debut for the club, starting in a forward position, against Shan United in the AFC Cup and scored his first goal, as well as setting up the third goal of the game, in a 3-0 win.[16] Two weeks later on 5 October 2023, he scored a brace in another AFC Cup match against Cebu, as well as, setting up one of the goals, in a 8-2 win.[17] Germain captained his first match as a Macarthur FC player against Central Coast Mariners on 29 October 2023, with captain Ulises Dávila placed on the bench and scored the opener, in a 2-1 win.[18] After the match, manager Mile Sterjovski praised his performance and hope that he continued to score more goals.[19] His impact at Macarthur FC was noticed by the Australian newspaper The Daily Telegraph.[20] Germain spoke out about settling in Australia with his wife and son.[21] He then scored his first hat-trick in Australia, in a 4-3 win against Western Sydney Wanderers on 4 February 2024.[22]