The 30-year-old mutually terminated his contract with Kotoko a fortnight ago following a confrontation with the club's chief executive officer Kwame Kyei.
“Accra Hearts of Oak are delighted to confirm that Ernest Sowah has signed for the club and will join his new teammates at training,” a club’s official statement said.
Hearts goalkeeping coach Jerry Agyei lauded the qualities of Sowah and believes he will help them reach their goals.
“We are happy to welcome Ernest Sowah into the Hearts family. He’s an experienced goalkeeper and we believe he will help bolster our goalkeeping department in our search for glory,” he told the club's website.
Sowah also expressed his excitement after completing the deal.
"I've signed a two-and-half-year contract and it's a happy moment for me because after several months on the sideline, I'll be playing in the top-flight again," Sowah told Goal.
"I'm aware that Hearts have issues with goalkeeping and I'm ready to team up with the other goalkeepers so that we can be able to solve it. There are a lot of things that we can achieve together so I'm ready to play my part wholeheartedly," he added.
Sowah becomes the second player to switch from Kotoko to Hearts this season after Evans Quao.