The deal, worth $1.3 million, according to The Associated Press, includes a vesting option for 2007.
Miller, 32, is 10-11 with a 4.66 ERA in seven seasons with Detroit, Houston, Philadelphia, the Los Angeles Dodgers, Toronto and Tampa Bay. He made 200 appearances out of the bullpen for the Blue Jays and Devil Rays from 2003-2005.
Last year Miller went 2-2 with a 4.06 ERA in 61 appearances with Tampa Bay. He became a free agent when the Devil Rays declined to tender him a contract by the Dec. 20 deadline.
Miller gives Houston a second left-hander to go with Mike Gallo in the bullpen.