Abstract Background Although global nutrition/dietary transition resulting from industrialisation and urbanisation has been identified as a major contributor to widespread trends of obesity, there is limited data in pregnant women, including those living with HIV in South Africa. We examined food-based dietary intake in pregnant women with and without HIV at first antenatal care (ANC) visit, and associations with maternal overweight/obesity and gestational weight gain (GWG). Methods In an urban South African community, consecutive women living with (n = 479) and without (n = 510) HIV were enrolled and prospectively followed to delivery. Interviewer-administered non-quantitative food frequency questionnaire was used to assess dietary intake (starch, protein, dairy, fruits, vegetables, legumes, oils/fats) at enrolment. Associations with maternal body mass index (BMI) and GWG were examined using logistic regression models. Results Among women (median age 29 years, IQR 25–34), the prevalence of obesity (BMI ≥ 30 kg/m²) at first ANC was 43% and that of excessive GWG (per IOM guidelines) was 37% overall; HIV prevalence was 48%. In women without HIV, consumption of potato (any preparation) (aOR 1.98, 95% CI 1.02–3.84) and pumpkin/butternut (aOR 2.13, 95% CI 1.29–3.49) for 1–3 days a week increased the odds of overweight/obesity compared to not consuming any; milk in tea/coffee (aOR 6.04, 95% CI 1.37–26.50) increased the odds of excessive GWG. Consumption of eggs (any) (aOR 0.52, 95% CI 0.32–0.86) for 1–3 days a week reduced the odds of overweight/obesity while peanut and nuts consumption for 4–7 days a week reduced the odds (aOR 0.34, 95% CI 0.14–0.80) of excessive GWG. In women with HIV, consumption of milk/yoghurt/maas to drink/on cereals (aOR 0.35, 95% CI 0.18–0.68), tomato (raw/cooked) (aOR 0.50, 95% CI 0.30–0.84), green beans (aOR 0.41, 95% CI 0.20–0.86), mixed vegetables (aOR 0.49, 95% CI 0.29–0.84) and legumes e.g. baked beans, lentils (aOR 0.50, 95% CI 0.28–0.86) for 4–7 days a week reduced the odds of overweight/obesity; tomato (raw/cooked) (aOR 0.48, 95% CI 0.24–0.96) and mixed vegetables (aOR 0.38, 95% CI 0.18–0.78) also reduced the odds of excessive GWG. Conclusions Diet modification may promote healthy weight in pregnant women living with and without HIV.