Mendoza is a 22-year-old forward who represented Colombia at the 2009 U-17 World Cup in Nigeria and 2011 U-20 South American championship in Peru.
The prolific striker was last playing for Colombian giants Deportivo Cali and will add plenty of quality and firepower to Chennaiyin FC's attack.
"We are delighted to add Mendoza to our squad which is looking well-balanced now. The team has been gelling well for the last couple of weeks with plenty of hard work put in by the players and support staff.
Chennaiyin's squad comprises 16 domestic players and 12 foreigners including player-manager Marco Materazzi, marquee foreigner Elano and former Manchester United defender Mikael Silvestre.
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Chennaiyin FC played a practice game against Army XI on Wednesday at the Bangalore Football Stadium and won 7-1 with Eduardo Silva and Bernard Mendy scoring twice while Abhishek Das, Cristian Hidalgo and Jaison Vales netting one each.
Chennaiyin FC faces the same opponents again on Friday.
The Chennai outfit start their Indian Super League campaign with an away fixture against FC Goa on October 15 while their first home assignment is against Kerala Blasters on October 21.