Born in Castiglione del Lago, Umbria, Italy to Nigerian parents who later obtained Italian citizenship, Okaka joined the Roma youth system in 2004.

[3] Okaka scored his first goal for Roma in a Coppa Italia match against Napoli on 8 December, with a powerful run from midfield and a precise shot to the left of the goalkeeper, making him the youngest goalscorer in the competition at the age of 16 years, 121 days.

[4][5][6] Okaka scored his first Serie A goal on 17 September 2006, concluding a 3–1 win over Siena, just 38 days after his 17th birthday, after coming on as a substitute for Francesco Totti.

[4] Okaka was subsequently loaned to Serie B side Modena for the 2007–08 season in order to gain some first team experience.

He made his debut in the 1–0 win over Portsmouth on 3 February, and scored his first goal for the club eleven days later in a 5th round FA Cup tie at home to Notts County.

In August 2011, Okaka was attacked by Roma fans after a training session for allegedly not wishing to sign autographs.

The following day he was loaned to the newly promoted Serie B club Spezia where he made 38 appearances, scoring seven goals and assisting six more.

[16] On 31 January 2014, Okaka was transferred to the fellow Serie A outfit Sampdoria on a permanent deal, with Nicola Pozzi moving the opposite direction.

[18] On 10 June 2015, the owner and president of Sampdoria Massimo Ferrero told the Italian media that Okaka would be leaving the club.

[24] He scored six goals in 16 games as the Bianconeri avoided relegation, including braces in consecutive wins over Frosinone and SPAL in May.

He made his debut as a substitute, replacing Sebastian Giovinco in the second half, and scored the only goal of the match in the victory at Sampdoria's home ground, the Stadio Luigi Ferraris.