The 24-year-old has been in fine form this season with eight goals in 17 appearances in the Bundesliga, helping Leverkusen to third place under Roger Schmidt.
Bellarabi's return makes him the top goalscorer at the club at the halfway stage in the season, and Leverkusen have acted quickly to tie him down.
In a message on their official Twitter account, the club said: "Bayer04 has exercised its option and the current contract with Karim Bellarabi [is] extended until 30 June 2017."
Bellarabi arrived at the BayArena in 2011 but, after recovering from injury, spent last season on loan at former club Eintracht Braunschweig.
He has excelled in his first uninterrupted campaign with Leverkusen, though, and was rewarded with his first senior Germany cap in October against Poland.
