The highly-rated defender will now stay at the Coral Windows Stadium until 25 October 2015. His previous deal expired after Sunday's Yorkshire derby with Sheffield United.
Burke, who turned 19 this month, is on loan to the Bantams from Premier League side West Ham United.
The defender has played every minute of all five of City's matches so far since his arrival - a spell of games which has seen Phil Parkinson's men go unbeaten.
Burke also netted his maiden senior goal for City during the 2-1 win at Oldham Athletic.
During his time with Parkinson's squad, Burke was recently capped at Under 20 level for England for the very first time.