Serran will join as the club's seventh and final foreign signing ahead of the fifth season of ISL. The 34-year-old had trained and played for Bengaluru FC during their Spanish preseason sojourn.
The Barcelona-born player is a product of Espanyol's youth system and has played three La Liga games during his stint at the club. He has also plied his trade in the English Championship with Swansea City from 2008-2011.
Serran becomes the fourth Spanish player at Bengaluru FC after Dimas Delgado, Juanan and Xisco Hernandez. Having retained Erik Paartalu and Miku from last season and signed Chencho Gyeltshen this summer, last year's ISL finalists have now filled their foreign player quota.