Effective secondary prevention of HIV infections requires knowledge about changes in sexual behaviors after diagnosis among people living with HIV (PLHIV), yet there is a dearth of literature assessing gender-specific patterns and correlates of such changes among heterosexual PLHIV in China. Data used in the current study were derived from a cross-sectional survey conducted from 2012 to 2013 among 1212 heterosexual sexually active PLHIV in Guangxi, China. Most participants reduced sexual frequency (71.2%), reduced or maintained the same number of sexual partners (96.6%), and increased or maintained same frequencies of condom use (80.6%). Gender difference was found in changes in sexual frequency, but not in the number of sexual partners or condom use. For males, decrease in sexual frequency was associated with having no desire to have children (OR = 2.03, 95% CI 1.20, 3.44), being virally suppressed (OR = 0.27, 95% CI 0.079, 0.94), and social support (OR = 1.44, 95% CI 1.06, 1.96). Health promoting behaviors in condom use (i.e., increased or maintained same frequencies of condom use) for males was associated with being 45 years of age or older (OR = 0.35, 95% CI 0.21, 0.61), having an HIV-negative main partner (OR = 1.80, 95% CI 1.11, 2.92), and physical health-related quality of life (OR = 1.02, 95% CI 1.00, 1.04). For females, decrease in sexual frequency was associated with having no desire to have children (OR = 1.58, 95% CI 1.01, 2.47). Health promoting behaviors in condom use for females was associated with having an HIV-negative main partner (OR = 3.24, 95% CI 1.63, 6.45) and social support (OR = 0.75, 95% CI 0.57, 0.99). Future intervention efforts need to target PLHIV who need extra support in making health-improvement efforts and to facilitate gender-specific behavioral changes in sexual risk reduction after HIV diagnosis.