[7][8][9] Born in Mendrisio, Ticino, an Italian-speaking canton, Switzerland, Martinelli moved south to Italy to start his professional career.

[15][16] On 25 July 2016, the loan was renewed,[17][18] and in August 2017 Martinelli signed for Brescia on a permanent basis.

As a regular, and also captaining the team in Mario Santana's absence, he won promotion to Serie C on his debut season with the Rosanero.

On 7 September 2020, Palermo announced Martinelli was forced to retire from active football due to cardiac issues.

He only played once for Swiss U19 team in competitive match in 2012 UEFA European Under-19 Football Championship elite qualification.