The forward, third-highest scorer in the German Bundesliga last season with 25 goals, moved on a reported loan with an option to buy.
The forward, third-highest scorer in the German Bundesliga last season with 25 goals, moved on a reported loan with an option to buy, just before the mid-season Chinese transfer window closes on Friday.
There was no immediate comment from Tianjin, who are coached by Italy's 2006 World Cup-winning captain Fabio Cannavaro and were previously strongly linked with Chelsea's unsettled Spanish striker Diego Costa.
Cologne did not disclose terms of the deal, but German daily Bild reported that Modeste moved on a two-year loan deal for six million euros with an option to buy him for 29 million euros.
"The 29-year-old will continue his career in the Chinese Super League with Tianjin Quanjian," said a Cologne statement.
"All relevant parties have reached an agreement. FC Cologne would like to thank Tony for his performances in the FC jersey whilst wishing him all the best for the future."
Modeste's 25-goal haul in the Bundesliga last season was bettered only by Borussia Dortmund's Pierre-Emerick Aubameyang (31) and Bayern Munich's Robert Lewandowski (30) as Cologne finished fifth in the table.
The move comes just two weeks after the much-rumoured transfer appeared to have fallen through. Reports in Germany said Modeste had been the subject of a 35-million-euro bid but Cologne said "the parties involved were not able to reach an agreement".
The terms of the new deal appear designed to get round a Chinese Football Association (CFA) rule intended to curb spending after a slew of big-money deals in the past year including Oscar's Asian transfer record move from Chelsea to Shanghai SIPG for 60 million euros.
The CFA have ruled that loss-making clubs need to pay a 100 percent levy on transfer fees with the proceeds going to a government-run fund promoting Chinese youth football.
Last month, as the summer transfer window opened, the CFA imposed the tax on transfers for foreign players costing more than 45 million yuan (5.8 million euros).
Tianjin Quanjian, who already have Brazilian forward Alexandre Pato and Belgian international Axel Witsel, have been chasing a star forward for months and were also linked with Aubameyang.
But they settled on Modeste, who started in French football and had an unhappy spell in England at Blackburn Rovers before moving to Germany.