The Hiroshima Carp of Japan's Nippon Professional Baseball have signed Montero to a contract, Yahoo Japan reports.
Montero cleared waivers Thursday and was sent outright to Triple-A Albuquerque.
The Rockies designated Montero for assignment Sunday.
Montero is not in the lineup for Tuesday's game in Houston.
Montero is out of the lineup for Sunday's game against the Pirates.
Montero will play first base and bat cleanup Saturday against Pittsburgh, Patrick Lyons of JustBaseball.com reports.
Montero is starting as the designated hitter and batting eighth for Friday's game against the Pirates.
Montero is out of the lineup for Monday's game against the Twins, Luke Zahlmann of The Denver Gazette reports.
Montero is out of the lineup for Sunday's game at St. Louis, Luke Zahlmann of The Denver Gazette reports.
Montero is out of the lineup for Sunday's game against the Dodgers, Luke Zahlmann of The Denver Gazette reports.