Myers is in his second season with the Astros. Roy Oswalt, who's now in Philadelphia, started Houston's last eight opening days.
Astros manager Brad Mills says he's "thrilled" with Myers as the opening day starter, adding "there's nobody else we would want there."
Myers went 14-8 with a 3.14 ERA in 2010, his first year with the Astros after pitching the previous eight years for the Phillies. The 30-year-old is 0-1 with a 9.00 ERA in four starts this spring.