The Liverpool forward created the first and scored the second during Tuesday night’s 2-0 win over FC Porto at Anfield in their quarter-final tie.
Firmino saw off competition from Son Heung-Min (Tottenham Hotspur), Gerard Pique (FC Barcelona) and Frenkie de Jong (Ajax) to take the prize.
The Reds take on Porto in the second leg of their last-eight clash at Estadio do Dragao next Wednesday.