Tianjin are managed by former Italy World Cup-winning defender Fabio Cannavaro who along with Pato confirmed the deal on social media. The terms were not disclosed.
The 27-year-old Pato joined Spanish side Villarreal last year and will link up with Belgian midfielder Alex Witsel at the newly promoted team.
CSL clubs have made a number of high-profile signings recently, with Shanghai SIPG buying Brazil midfielder Oscar from Chelsea for 60 million euros ($64.5 million).
Shanghai Shenhua signed Argentine striker Carlos Tevez for a reported 84 million euros.
(Reporting by Sudipto Ganguly in Mumbai; editing by Ed Osmond)
