Early career Nsereko was born in
Kampala and started his career at
1860 Munich. He was signed by
Brescia in the summer of 2005, aged 16, the minimum age limit allowed by
FIFA for international transfer among
European Union nations. He made his first team debut during
2005–06 Serie B season against
Crotone, the last match of the season. He made 23 appearances for Brescia in all competitions, scoring three goals, before signing for West Ham.
West Ham United On 26 January 2009, Nsereko signed for
West Ham United for an undisclosed fee, thought to have been in the region of £9 million dependent on appearances and other factors, on a four-and-a-half-year contract. His English football, Premier League and
West Ham debut came on 28 January 2009 in West Ham's 2–0 home win against
Hull City. West Ham retain the rights to 50 percent of the player's sell-on fee. Nsereko never broke into the first team and in January 2010 was loaned out to
Bologna, in what proved to be another disappointing experience, with only two appearances with the
Rossoblu. In July 2010, he was sent back to Germany, joining
2. Bundesliga side
TSV 1860 Munich on a season loan; the loan agreement was however cancelled unilaterally on 23 October 2010, after the player was reported missing for a week before being found at his sister's place. In January 2011, Nsereko joined Bulgarian
A PFG side
Chernomorets Burgas on loan until the end of the season. After this loan spell, he was loaned again this time to
Serie B side
Juve Stabia. After only one game with the club, Savio was reported missing once again in September 2011, leading his club to ask for unilateral rescission of the contract. He was successively reported being in London, and, after returning to Italy with a medical certificate only two weeks later, he was allowed to leave to Germany to deal with unspecified personal problems. In January 2012, Nsereko joined Romanian Liga I side
FC Vaslui on loan until 31 December 2012. In July 2012, it was reported in Germany that Nsereko joined
3. Liga side
SpVgg Unterhaching on loan for a season.
SpVgg Unterhaching After months of speculation, Nsereko finally moved
SpVgg Unterhaching of the third division in Germany on 3 September 2012 for free. In an interview on the club's website, Nsereko cited his desire to play in his home town of Munich as one of the motivating factors for his move. He was released by Unterhaching after 2 months with the club. Fiorentina also stated in its financial report ending on 31 December 2012, that Savio was released due to breach of contract on Savio's side. Fiorentina had rights to claim damages for Savio's residual contract which ending on 30 June 2016. It was reported that Savio faked his own kidnapping in Thailand.
FC Atyrau On 24 December 2013, Savio signed an 18-month contract with
Kazakhstan Premier League side
FC Atyrau. On 15 March 2014, he made his
Kazakhstan Premier League debut and scored the winning goal for his team in the 1:0 away victory over
FC Kairat. In June 2014 after 10 appearances for the club, Savio executed a clause in his contract allowing him to leave Atyrau going on to have a trial with
Anzhi Makhachkala at the end of the month. At the end of the
2014 season, Savio's only goal for Atyrau was voted as
Goal of the Season by the club's fans. Savio returned to Kazakhstan in December 2014, joining
FC Irtysh Pavlodar on trial, but failed to win a contract, going on trial with
Beroe of the
Bulgarian A Group in late January 2015, eventually joining the club. In February 2016, Savio went on trial with
Kazakhstan Premier League side
FC Shakhter Karagandy, but wasn't offered a contract.
Lietava Jonava On 17 March 2016,
Lietava announced the signing of Savio. Four months later, 18 July 2016, Savio's contract with Lietava was terminated by mutual consent.
Later years In May 2017 it was unveiled Nsereko had been signed by German amateurs
FC Pipinsried for the new season. His contract got terminated on 21 July 2017, because they couldn't agree on several terms. In January 2018, Nsereko went on trial with
FC Vereya, signing with the club shortly after. He left the club in April. In the summer of 2018, Nsereko joined
Armin München as a youth coach. During his time at SC Armin, Nsereko made two friendly appearances for the club, as well as training with the first team. On 10 March 2019, Nsereko made his debut for the club, scoring twice in a 5–0 win against Fürstenri II. Nsereko finished the
2018–19 season with seven goals in as many games. Following 14 further goals in 12 games the
following season, Nsereko joined
BSC Sendling. Nsereko also joined BSC Sendling's second team as manager. ==International career==