In many developing countries, labor force participation by women in the childbearing years has increased rapidly. Social and economic changes present new challenges for women attempting to combine their roles as workers and mothers. Little is known about how these challenges affect infant feeding choices. This multidisciplinary study investigated work and infant feeding decisions among 313 employed women in Chiang Mai, Thailand. Resumption of employment generally had negative affects on breastfeeding rates and duration. At 6 months postpartum, women who worked inside the home breastfed more than those working in the formal sector at jobs with inflexible hours (home, 80%; public sector, 37%; private sector, 39%). Women who were working outside the home for a long period or had shift jobs encountered many obstacles to maintaining breastfeeding, and most gave it up within 1 month after resuming employment. There is a need for multisectoral policies that address obstacles to breastfeeding among women in the paid labor force in Thailand.