Veart, who was appointed interim coach in 2020 before receiving the permanent role, is the second coach sacked this season after Newcastle Jets counterpart Rob Stanton.
He enjoyed a red-hot start to the season, his fifth at the helm full-time, with Adelaide in early premiership contention.
But the Reds have since plummeted to outside the top six amid a seven-game winless run, including Saturday's dramatic 3-2 loss to fellow finals contenders Sydney FC.
Adelaide are outside the top six on goal difference alone with four games to go, starting with Saturday's away trip to Perth.
South Australian Veart has a long connection to the club, having also scored Adelaide's first goal in the inaugural ALM season in 2005-06.
Across his tenure, he was known for bringing through top local talents, headlined by Socceroos winger Nestory Irankunda.
"Carl's legacy at Adelaide United is undeniable. He has led this club with integrity, resilience, and a deep connection to our community, and for that, we owe him our heartfelt thanks," Adelaide owner Cor Adriaanse said in a statement.
"The club has exercised a contractual option not to extend his tenure beyond the current campaign.
"Change is never easy, but it is a natural part of growth. This decision has been made as part of a broader long-term strategy - one that Carl has helped shape.
"We are entering an exciting new chapter, built on the strong foundations he has laid, and we remain fully committed to our identity as a proud South Australian club.
"Carl Veart will always be a true Red, and he departs with the utmost respect and gratitude from everyone at Adelaide United."
Veart's departure seemingly opens the door for the Reds to have a shot at his former assistant Mark Milligan, who is widely expected to be appointed Newcastle boss.
They have also been linked to moves for Western United's John Aloisi and his brother and former Brisbane Roar coach Ross, who is Kevin Muscat's assistant at Shanghai Port.
29°C