Tuohy earned the long-term deal after producing solid form in his first season under Mick Malthouse.
The 23-year-old is in his fourth AFL season but his firston the Blues' primary list after three years as an international rookie.
The long-kicking Tuohy has played 40 AFL games, including all 10 this season as a lockdown defender.
Carlton football manager Andrew McKay said the deal gave Tuohy the chance to extend his "tremendous journey".
“AFL is a hard game to learn when you haven’t grown up with it," he told carltonfc.com.au. "To come over here as a rookie, learn the game, and be promoted to the senior list is a fantastic effort.
“We are really pleased with the progress Zach has made, and even more pleased that he has committed to Carlton for another three years.”
