Emmanuel consequently, went on trial with Charlton Athletic and Brentford. He signed his first professional deal with the latter in May 2008. His transfer fee was reportedly £2,500, paid by the Brentford fanzine "Thorne in the Side".
The striker was loaned to Conference South side Welling United in November 2008, but was recalled by Brentford without making an appearance. He returned to Park View Road in December 2008, and made four appearances in the league, scoring once. The loan spell was extended for a further month in early January 2009, but just three days later, the decision was reversed, and Ademola returned to Griffin Park.
Emmanuel joined Woking on loan the following season. On 29 January 2010, he made his loan move permanent by signing a contract with Woking, then staying on for the 2010–11 season. In July 2011, it was confirmed that Ademola would be spending another season at the club.
On 12 July 2012, Emmanuel joined another Conference South club, Eastleigh. He left Eastleigh on 27 November for divisional rivals Dover Athletic, while being the club's joint top scorer for the 2012–13 season having scored 7 goals in 15 league appearances. He left the club in May 2014 after turning down a new contract and subsequently joining Bromley. After scoring three times in pre-season, Ademola scored Bromley's opening goal of the league season, in a 3–1 away win against Havant & Waterlooville. He was a key figure in Bromley's title winning season in 2014–15, and continued his fine form in the National League, including a hattrick in a 7–3 victory over Torquay United. He left Bromley after his contract expired in the summer of 2016.
Dover Athletic
After a two-week trial at Gillingham, Emmanuel eventually re-signed for Dover Athletic on 5 Aug 2016.
In May 2017, Emmanuel signed a deal with Sutton United. He made his club debut on 8 August 2017 in a 1–0 away defeat to Eastleigh before scoring his first goal for the U's on 15 August in a 2–1 home victory over Macclesfield Town. He joined Maidenhead United on loan in October 2017.
Emmanuel joined Billericay Town for the 2018-19 season. In his first season at the club, he scored 25 goals - 17 in the league and 8 in cup competitions - and finished the season as the club's top scorer. In total, he scored 30 goals in 63 games for Billericay.
Welling United
Emmanuel joined Welling United on 22 November 2019.
Wealdstone
After seven appearances for Welling, Emmanuel joined Wealdstone on 10 January 2020.
