He is the older brother of Khairul Nizam who was a former footballer who played as a winger or striker for Singapore Premier League club Tanjong Pagar United F.C.

Along with Baihakki Khaizan, Shahril Ishak and Hassan Sunny, Khairul Amri was in the pioneer batch of the National Football Academy graduates in 2000.

However, he sustained a metatarsal injury in the 88th minute of the third-place play-offs of the 2008 Singapore Cup against his former club, the Young Lions, which ultimately ruled him out of action for two months.

In 2010, Khairul Amri moved overseas for the first time to join Indonesian football club Persiba Balikpapan.

Due to the severity of the injury, Khairul Amri's stint with the Indonesian Super League side was a short-lived one.

[5] The injury however, proved a serious issue as the club could not afford to keep Khairul Amri on the sidelines for an extended period of time.

During his recovery from the knee injury, Khairul Amri spent his time recuperating with Gombak United, at the offer of club chairman John Yap.

In November 2011, Khairul Amri agreed to join the LionsXII squad and played for the club in the 2012 Malaysia Super League (MSL).

He started the 2015 Malaysia Super League strongly, scoring 10 goals in 25 appearances for his team, including a hat-trick in a 4–1 win against Sime Darby.

[7] After an early end to his two-year contract with the Young Lions, Amri was chased by a few sides, including Tampines and Hougang United.

On 6 April 2023, Amri, the oldest outfield player in the 2023 Singapore Premier League at age 38, eluded the Hougang defence just enough to launch a spectacular scissors-kick volley to sweep the ball home.

[30] He scored the late winner in the second leg of the final against Thailand, helping Singapore to clinch their third AFF Championship title.

In 2011, Khairul Amri was unable to participate in the 2014 World Cup qualifiers because of the injury he sustained when he was playing for his club.

He was in the winning squad of the 2012 AFF Championship, scoring a free-kick 30 yards from goal against Laos, Philippines and also netting against Thailand in the final.