The pair's first professional deals were due to expire in the summer but they are now tied to St Andrews for a further two years.
Both Barrowman and Sadler (pictured) have appeared for the first team and are tipped for a bright future with Blues.
Barrowman made his Blues debut earlier this season while he has also enjoyed a loan spell in the First Division with Crewe Alexandra.
The forward's young team-mate Sadler has a handful of Birmingham outings to his name and the left back also played for Northampton Town on loan this term.
In addition to the duo extending their Blues careers, four Academy players have signed their maiden professional contracts.
Carl Motteram, Colin Doyle and Sam Alsop have inked two-year deals while Chris Cottrill has penned terms for 12 months.
