Myers, 29, who was just 4-3 with a 4.84 earned run average in 18 appearances (10 starts) in an injury-shortened season last year, will pay him $3.1 million in 2010 plus award bonuses.
The right-hander will make $8 million if the Astros pick up an option on the 2011 season, or Myers will receive a $2 million buyout.
Myers has spent his entire eight-season career with Philadelphia after being drafted by Wade, who was then with the Phillies.
"We're fortunate to be able to add someone of Brett's ability, particularly at this stage of the off-season," Wade said. "Brett has performed in a high visibility arena in Philadelphia and brings quite a bit of experience to the Astros. He's got a 68-57 (.544) record as a starter and will only be 29 years old for most of the 2010 season."