Metabolic syndrome (MS), a group of interrelated risk factors for cardiovascular diseases (CVD) and type 2 diabetes, has been increasingly reported among HIV-infected patients. Data on the prevalence and risk factors for MS among HIV-1 infected Thai adults are limited. The study collected cross-sectional data from 580 HIV-1 infected adults-46.2% were men and 71% were antiretroviral therapy (ART)-experienced. The majority (78.8%) of them used non-nucleoside reverse transcriptase inhibitor-based regimens. Data on lipid profiles, fasting blood glucose, CD4 count, HIV RNA, antiretroviral therapy (ART), anthropometry, food intake, and exercise were recorded. MS was defined using American Heart Association/National Heart Lung and Blood Institute criteria. Overall prevalence of MS was 22.2%; 15.9% in ART-naïve group vs. 24.9% in ART-experienced group, p = 0.018. Significant risk factors for MS in multivariate analyses included age ≥35 years (odds ratio, OR, 4.2, 95%CI 1.6-11.0, p = 0.004), high cholesterol (OR 4.7, 95%CI 1.7-12.9, p = 0.002), and living outside Bangkok (OR 4.2, 95%CI 1.6-10.8, p = 0.003) in the ART-naïve group, and female gender (OR 1.7, 95%CI 1.0-2.8, p = 0.05), lipodystrophy (OR 1.8, 95%CI 1.0-3.0, p = 0.032), high cholesterol (OR 1.9, 95%CI 1.1-3.1, p = 0.015), and food insecurity (OR 1.8, 95%CI 1.0-3.3, p = 0.05) in the ART-experienced group. All variables, except for female gender in the ART-experienced group, remained significantly associated with MS in a model where lipodystrophy was excluded. We concluded that MS was common among HIV-1-infected Thai adults. As HIV-infected patients get older, early screening and intervention, such as ART modification to avoid lipodystrophy, may reduce MS and CVD-related morbidities and mortalities in long-term care.