The deal reportedly is for $5.5 million.
Aoki had been a non-tender candidate. The Astros had claimed him off waivers from the Seattle Mariners on Nov. 3.
Aoki, 34, played in only 118 games in the majors last season for Seattle, batting .283 in 417 at-bats. Aoki also spent 24 games at Triple-A Tacoma.