Data for this study were obtained from 2375 tuberculosis (TB) patients registered during 2007-2009 and 43 health providers to examine the trend of TB patient referral for HIV (human immunodeficiency virus) testing and to investigate provider-associated barriers to the referral in Prey Kabas operational district, Takeo province, Cambodia. Referral rate for HIV testing was 4.4% (30/684) in 2007, 15.4% (116/751) in 2008, and 30.1% (283/940) in 2009, with a significant upward trend over the period of time (P = .009). The main barriers perceived by health providers were poor knowledge about TB/HIV, lack of communication skills, absence of any target plan for TB patient referral for HIV testing, and fear associated with informing positive test results to the TB patients and the associated stigma. Strategies to raise awareness about HIV/AIDS/TB among TB patients and their providers may improve the current state of low referral and its barriers in Cambodia.