The 24-year-old, currently with the Japan team in Florida preparing for the 2014 FIFA World Cup™ in Brazil, will sign a deal taking him through until June 2017 subject to a medical, Cologne said on their website. Terms were not disclosed.
"It's a relief to get the move before the World Cup," said Osako, who joined 1860 from J-League side Kashima Antlers in the January transfer window. "For me the Bundesliga is one of the best in the world and I'm sure I can keep improving in Germany," he told Japanese reporters in Florida.
Osako, likely to start on the bench for Japan in Brazil, appeared in 15 games for 1860, scoring six goals.
"It's given me something else to look forward to before the World Cup," added Osako, who has three goals in eight games for his country. "But first I have to give everything for Japan and hopefully take some good form to my new team."
The deal comes after Japan captain Makoto Hasebe signed a two-year contract with fellow Bundesliga team Eintracht Frankfurt from relegated Nuremberg.
The 30-year-old joined Germany's top-flight in 2007/08 from J-League side Urawa Red Diamonds and has made 135 Bundesliga appearances, scoring five goals.