The 25-year-old striker inherited the responsibility from Petrov after the Bulgarian was diagnosed with acute leukaemia following Villa's 3-0 defeat to Arsenal in March.
Agbonlahor told the club's official website: "I've matured as a player so the prospect of being captain isn't as daunting as it might have been a couple of years ago.
"It obviously a big thing for me. Maybe it's not something I imagined when I first broke into the team, but it's a privilege to be following some great Villa captains.
||Gabriel Agbonlahor is 5/1 with PaddyPower to score anytime for Aston Villa against Manchester United
The England international insists that the Bulgarian will resume his duties as skipper if he makes a return to playing.
"I've known Stilian for nearly six years and he's a fighter so I'm confident he will come through this," Agbonlahor added.
"The really difficult thing to take in is that Stilian was in better condition than most players when the diagnosis was made.
"We will all give 100 per cent and try to get a result for Stan in every game from now until the end of the season."
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