Despite expanding sexually transmitted epidemics in South China, the majority of patients presenting to sexually transmitted infection (STI) clinics are not routinely screened for HIV infection. Identifying barriers to offering HIV testing among STI care providers is an important public health priority. The aim of this study was to investigate the frequency of offering HIV testing among STI care providers in South China and reported physician barriers to offering HIV testing. More detailed operational data regarding HIV test offer frequency and barriers to testing may enhance routine HIV testing at STI clinics. A sample of 62 STI care providers within the Pearl River Delta Region of South China completed a survey including socio-demographic and training background information (including sex, age, medical education, year of terminal medical degree, and HIV-specific training), reasons for not offering HIV testing routinely, and physical examination and sexual history taking practices. Frequency of offering HIV testing was calculated based on reports from research assistants and operational data. STI care providers offered HIV testing to 3011/10,592 (28.4%) of their patients. There was substantial variability across providers in the frequency of offering testing, ranging from 3 to 100%. None of the identified physician factors were associated with offering HIV testing 100% of the time in the multivariate model. The most commonly physician reported barriers to HIV testing included: (1) low perceived prevalence of disease and (2) not recommended by current guidelines. Forty-seven providers (76%) reported asking about same sex behaviors rarely or never. Further research on HIV screening practices of STI care providers may help scale up HIV provider-initiated testing and counseling programs.