The lock – who is Welsh-qualified – will link-up with Dean Ryan’s men with immediate effect having signed a long-term contract at the region.
“We’re really pleased to bring Joe, a Welsh-qualified player, to the region and look forward to him developing in our environment,” said Ryan.
“Joe is hungry to prove himself here, improve as a player, and take the opportunity that we have given him with us.”
Maksymiw started his career in the Leicester Tigers Academy and made his debut for the English club against the Barbarians in 2014. He later made his English Premiership debut in September 2017 against Gloucester.
The 24-year-old – who is 6ft 8in and weighs 18st and 2lbs – moved to Connacht in 2018 and made 25 appearances over two seasons in Galway.
Maksymiw said: “I’m thrilled to have signed for Dragons. The region is clearly on the up so it is an exciting time to be joining and coming to Wales.
“I’m now looking forward to continuing to develop my game under Dean, Luke Narraway and the other coaches.
“I can’t wait to get stuck in with the lads and start contributing to the region, both on and off the pitch”.