Infection after anterior cruciate ligament (ACL) reconstruction is a rare but devastating complication. Articular cartilage damage, a function of the duration of the infection and the virulence of the infecting organism, is largely responsible for poor functional outcome. Rapid diagnosis and treatment is therefore essential. We discuss the diagnostic dilemmas of differentiating infection from normal early postoperative ACL recovery, and the treatment options for both intra-articular and extra-articular infections, including graft salvage. Finally, the expected functional outcomes in patients treated for intra-articular infection after ACL reconstruction are also discussed.