The 20-year-old, who is yet to make his senior debut despite appearing several times in matchday squads, has signed up for the next two years.
Johnson spent time on loan at Yeovil last season, but his aim now is to follow fellow academy graduates Nathan Baker, Ciaran Clark and Andreas Weimann into the Villa first team.
He told the club's official website: "Having guys like Andi, Ciaran and Nathan get into the first team is definitely an inspiration because they've been in the position I'm in.
"They kicked on and they got into the team and look at them now, they're Premier League players. That's obviously where I want to be.
"I'm really happy to have signed the new contract. These are exciting times at the Club at the moment, you can see where the manager wants to go with it and what he's trying to do and it's really good.
"I'm really looking forward to coming back into training and I'm hoping that this year can be even better for me and for the team."