Doyle has signed a two-year deal, and will become the club's thirteenth arrival during the transfer window so far.
After John McLaughlin moved to Sunderland earlier this summer, Hearts have been on the lookout for a replacement.
Doyle will join Zdenek Zlamal and Kevin Silva as the third addition to the goalkeeping sector.
The 33-year-old shot stopper made 88 appearances for Bradford over the two seasons spent there, helping them reach the League 1 play-off final in 2017.
He began his career with Birmingham City, but has also had spells with Nottingham Forest, Millwall and Blackpool.
He has received four caps from Ireland, and his most recent came from a 2-0 defeat against World Cup champions France in May this year.