The Black Cats have handed the midfielder a long-term contract and the number 29 shirt, with Ahoka becoming Sunderland's third signing of the summer following the arrivals of Thomas Meunier and Dayann Methalie.
He originally moved to Antwerp from AC Normands in his native DR Congo, and impressed enough in the Belgian top flight to attract Premier League interest before his 21st birthday.
"It's an exciting start for me," Ahoka said. "I've always watched the Premier League on TV and I'm thrilled to be here. Now, it's up to me to give everything I can to help the club go as far as possible."
Ahoka credited the difficulties of relocating from Africa to Europe with accelerating his development.
"At first it was difficult for me to come from Africa and play in Europe, but I applied myself to the process and overcame those hurdles," he explained. "I worked hard in training and started the season and played well."
He will link up with fellow DR Congo international Noah Sadiki, already an established figure in Sunderland's squad.
"I'm really happy to be here with Noah – he's a good friend and that's really useful," Ahoka said. "We didn't get to play together for the Congo national team, as they had left for the tournament before I was subsequently called up, but I'm really happy to get together now."
The midfielder is also looking forward to learning from Sunderland captain Granit Xhaka, one of the most experienced midfielders in the Premier League.
"I've still got a lot of learning to do, so I can do that from watching how Granit and Noah play as I learn to adapt," he said.
Sunderland's director of football, Florent Ghisolfi, identified Ahoka as a target after his performances for DR Congo's youth side at the Toulon Tournament this summer, where he won the competition's Revelation Award.
His arrival takes the number of African players in Sunderland's squad to seven, alongside Morocco's Chemsdine Talbi, Mozambique's Reinildo, Senegal's Habib Diarra, and Ivory Coast pair Simon Adingra and Jocelin Ta Bi.
Regarded as a defensive midfielder by trade, Ahoka is also comfortable filling in at centre-back and is expected to serve initially as understudy to the 33-year-old Xhaka, who is unlikely to play every midweek fixture across a season that includes Europa League football.