The 20-year-old joined the 'Gunners' back in 2016 and has since spent time on loan in Holland, first with MVV Maastricht where he scored three times in 34 appearances in the Eerste Divisie.
A step up to the Eredivisie followed as he joined VVV-Venlo on another loan deal, this time scoring once in 11 appearances.
Born in Nigeria, Nwakali first rose to prominence with his performances at the 2015 U17 World Cup, where he won the Golden Ball.
Speaking to Porto's official website, Nwakali explained his reasons for making the switch to Porto.
"My main goal is to develop, improve my qualities and the other aspects I know I need to correct to grow in the way I play," he said.
"I think FC Porto is the right place to evolve as a player. There are good players, young people, and I think I'll grow up here."
19 July 2018