He is a product of Aston Villa's Academy, and made his first-team debut in 2006 following loans to Football League clubs Watford and Sheffield Wednesday.

[5] On 22 September 2005, he was loaned to Championship club Watford,[5] where he made his senior debut six days later, replacing Trevor Benjamin at half time in a 3–1 defeat away to Coventry City.

O'Leary was forced to delve into the youth academy because of a lack of senior strikers due to injury, thus earning Agbonlahor a rare start.

[10] In five pre-season matches of the 2006–07 season, Agbonlahor netted three goals for Aston Villa; a quick double salvo against Walsall (the first a near-post header, the latter a close range finish) in a 5–0 victory,[11] and a consolation strike in a 2–1 defeat at NEC.

[14] On 30 September, Agbonlahor scored a crucial equaliser against Premiership champions Chelsea just before half-time, heading in Liam Ridgewell's cross with a glancing header to earn Villa a 1–1 draw.

[18] Agbonlahor then scored deep into injury time in the following match, against Watford on 20 January 2007, to end a Villa winless run that stretched back to 11 November.

[23] The following Saturday, in the absence of John Carew, he was moved back to his natural position at centre forward and again found his name on the scoresheet.

[24] Agbonlahor made it three in a row on Easter Monday, again scoring an equaliser, adjudged to have crossed the line by assistant referee Dave Richardson.

[26] Agbonlahor headed the winning goal in the 86th minute of the Second City derby away to Birmingham on 11 November, shortly after saving the ball on the line from a Liam Ridgewell shot.

The three goals were netted in the space of seven minutes, making it the third-fastest hat-trick in the history of the Premier League after Robbie Fowler and Sadio Mané.

Some fans began to get frustrated with Agbonlahor, and in Villa's home defeat against Tottenham Hotspur, there were some sarcastic cheers as he was substituted off by Martin O'Neill.

[51] Fellow Villa forward Emile Heskey played the ball into the penalty area where Agbonlahor turned a defender and placed a low shot past Wolves goalkeeper Wayne Hennessey.

[56] Despite Villa suffering some issues on and off the field at the beginning of the season, such as the resignation of manager Martin O'Neill and a humiliating 6–0 defeat at the hands of Newcastle United, Agbonlahor defended the club and stated his intent to remain there for the long term.

[58] On 16 January 2011, he made his 200th appearance in an Aston Villa shirt in a 1–1 draw with rivals Birmingham, playing the full 90 minutes at St Andrew's.

[62] Agbonlahor scored his first goal of the 2011–12 season in Aston Villa's 3–1 home win over Blackburn Rovers on 20 August 2011, and followed this up with the leveller in a 2–2 away draw against Everton ten days later.

After rediscovering his goalscoring form under new boss Alex McLeish, the striker publicly spoke of his discontent at the managerial tenure of Gérard Houllier and his assistant Gary McAllister and said that he even considered quitting the club had the previous regime remained.

[67] Meanwhile, on the pitch Agbonlahor continued to impress, scoring the first goal and setting up Darren Bent for the second in a man of the match performance against Wigan on 1 October.

[79][80] This resulted in strong praise from manager Paul Lambert, and a huge demand from the public for an England call up, which was ignored by Roy Hodgson.

[84] Agbonlahor was given a straight red card on 20 December for a challenge on former teammate Ashley Young as Villa drew 1–1 with Manchester United,[85] however his three-match suspension was rescinded on appeal three days later.

[87] On 30 May in the FA Cup Final against Arsenal at Wembley Stadium, manager Tim Sherwood chose to start Charles N'Zogbia instead of Agbonlahor, and then brought him on in place of the Frenchman after 53 minutes, with Villa already 2–0 down; they eventually lost 4–0.

[90] Agbonlahor returned to the squad in an FA Cup tie against Manchester City on 30 January 2016,[91] and scored his first goal of the season a week later in a Premier League match in a 2–0 home victory against Norwich.

[92] On 1 April 2016, Aston Villa suspended Agbonlahor, pending an investigation into reports that he was pictured appearing to hold a shisha pipe while on holiday in Dubai.

[95] Agbonlahor failed to impress new manager Roberto Di Matteo in pre-season, and his lack of involvement led to media speculation of a move away from the club.

When manager Steve Bruce arrived, he immediately reinstated Agbonlahor into first-team training, saying that he's "not interested in what has happened in the past" and that it's a "clean slate" for him.

[115] On 7 March 2007, Agbonlahor was one of several surprise names called up as part of a 37-man provisional Nigeria squad by new manager Berti Vogts, alongside fellow English players Victor Anichebe and Carl Ikeme, and full Israel international Toto Tamuz.

[116] On 1 February 2008, Agbonlahor was named in Fabio Capello's 23-man England squad to play Switzerland later in the month,[117] although a hamstring injury forced him to withdraw from the match.

[124] He made his first appearance in a competitive international on 14 October 2009, playing 66 minutes in the 3–0 win over Belarus in the last match of qualification for the 2010 World Cup.

In 2009, ahead of the striker's 23rd birthday, his mother made a public appeal to him via the city's Sunday Mercury newspaper in order to become part of his life once more.