Chairman Jeremy Peace told the club's official website: "We're delighted both Tony and Mark Venus have signed their new contracts. The new deals are just reward for their efforts over the past 16 months.
"We believe Tony is one of the brightest managerial prospects around and we're really pleased to have secured his services for a further three-and-a-half years.
"It's up to us to make sure we keep him focused and motivated, which we've moved to do by offering him this contract and giving him the platform to bring success here."
Mowbray himself added: "I'm delighted to sign this deal. I've enjoyed the challenge of the last 16 months of trying to get the club back to where we all feel it belongs.
"The club has shown faith in what we're trying to achieve by offering us these deals and, with the continued backing of the board, we will strive to continually improve the football club."