We evaluated the risk of human immunodeficiency virus (HIV) transmission among serodiscordant couples with low adherence to antiretroviral therapy (ART).Data of heterosexual couples/partners in 2010 were extracted from an Internet-based system. Participants were then followed over the course of a year with 6- and 12-month assessments. Prevalence and density of HIV seroconversion were calculated for spouses/partners who did not have a positive HIV test results at baseline. We calculated the transmission odds ratio (OR) value stratified by personal characteristics and behavioral correlates at 6- and 12-month follow-up, as well as seroconversion in spouses/partners over the year.A total of 5544 HIV/AIDS patients and their spouses/partners were recruited in this cohort. Incidence of HIV seroconversion among HIV-negative spouse/partner was 63.7/100 person years (PYs) (430/674.9) at the 6-month follow-up and 33.2/100PYs (567/1707.1PYs) at 12 months. The OR value of transmission from female to male was 2.1 times higher than from male to females at 6 months and 2.3 times higher at 12 months (P < .001). The 55- to 64-year age group was most likely to transmit HIV to their spouses/partners, 2.2 times greater than the participants who were 65 years and older. Married participants were 2.4 times higher at 6 months and 2.5 times higher at 12 months to transmit HIV than divorced/widowed participants. Lastly, transmission among illiterate participants was 6.7 times higher at 6 months and 2.3 times higher at 12 months than those with an educational attainment of community college or above.High HIV seroconversion was observed in this cohort. Spouses/partners who were male had the highest risk of HIV acquisition; those aged 55 to 64 years, having married status, and are HIV-positive with less education were more likely to transmit HIV.