Amaro just completed his 10th season as assistant GM and replaces the retiring Pat Gillick. Amaro was considered the front-runner for the job after Gillick said last year this would be his last season.
The Phillies are introducing Amaro at a Monday morning news conference. Last week, the team beat the Tampa Bay Rays to capture the second championship in franchise history.
The 43-year-old Amaro worked under former GM Ed Wade for seven seasons and the last three with Gillick. Amaro got the nod over Mike Arbuckle, who spent the last 15 years with the Phillies.