This study explored the association between mothers’ work-related factors and breastfeeding practices in Bangkok, Thailand. Data were collected from 84 working mothers with a child aged 6 to 24 months who visited the breastfeeding mobile clinic at a nursery goods exhibition. Thai interviewers collected data using a structured questionnaire. Analysis of the data showed that exclusive breastfeeding for 3 months was 78.6%, and for 6 months it was 38.1%. Mothers who returned to work 3 months or more after giving birth exclusively breastfed more than the mothers who returned to work in less than 3 months (crude odds ratio [OR] = 4.26, 95% confidence interval [CI] = 1.39-13.05; adjusted OR = 4.15, 95% CI = 1.15-14.95). Moreover, mothers who worked at self-employed or family-owned businesses and some mothers working at private companies showed tendencies of returning to work in less than 3 months. Results suggest that longer maternity leave would help extend the duration of exclusive breastfeeding. In addition, the improvement of a breastfeeding supportive environment in the workplace would be valuable and may be an effective means to improve breastfeeding practices and infant health.