|Date of birth||13 March 1975|
|Place of birth||Enugu, Nigeria|
|Height||1.85 m (6 ft 1 in)|
|1988–1989||NITEL Vasco Gama|
|1989–1990||African Continental Bank|
|1996–1997||→ Ourense (loan)||9||(0)|
|2003–2005||FC St. Pauli||38||(8)|
|* Senior club appearances and goals counted for the domestic league only.
Agu was born in Enugu, and began his career in his country with Bendel United, Enugu Rangers and Bendel Insurance FC. During his development years, he was considered to be the most promising footballer in the nation.
At the age of 19, Agu moved abroad joining Club Bolívar in Bolivia, having no impact whatsoever in one season.
In 1995, Agu ventured to Spain, joining La Liga side SD Compostela. The club's chairman José María Caneda described him as "...a mix between Ronaldo and Bent Christensen" (the latter a player in the team). During his stint, he shared teams with countryman Christopher Ohen but played only eight times in the season, going scoreless in the process.
Agu played the following eight years in Germany, starting with FSV Optik Rathenow in the NOFV-Oberliga. In his only season he scored a career-high 14 league goals, and his performances resulted in a move to SC Fortuna Köln in the 2. Bundesliga. In the following campaign, after failing to find the net, he signed with fellow league side FC Gütersloh; his spell would be short-lived, however, due to the club temporarily dissolving because of debt.
In 2000, Agu joined 1. FC Schweinfurt 05 in the Regionalliga Süd, scoring 11 goals in his first year as the club promoted to the second level. He was not re-signed however, and subsequently stayed in the category to play for VfR Aalen, netting 14 times as the Baden-Württemberg team finished in fourth place, three points shy of promotion.
In the 2002 summer, Agu returned to the second division signing for SV Wacker Burghausen. However, he failed to replicate his previous goalscoring record and was ultimately released at the end of the season. Afterwards, he played with FC St. Pauli in the Regionalliga Nord, scoring six goals in his first year but only two in the following.
- "¿Qué fue de... Festus Agu?" [Whatever happened to... Festus Agu?] (in Spanish). El Correo Gallego. 12 June 2009. Retrieved 21 October 2009.
- "RL Süd – Spieltag / Tabelle 2000/01" (in German). kicker. Retrieved 27 October 2011.
- "RL Süd – Spieltag / Tabelle 2001/02" (in German). kicker. Retrieved 27 October 2011.