Background: Working status is identified as a major risk factor of poor breastfeeding practices among workers. This study aimed to evaluate the knowledge, attitude, and factors associated with breastfeeding practice among white-collar and blue-collar workers in Indonesia. Methods: A cross-sectional study was performed in two factories and three government offices in Jakarta from December 2015 to February 2016. Subjects were woman workers whose children were age 6 to 24 months old and actively working in the factory and/or office. The factors studied were selected socio-demographic and occupational characteristics, score on knowledge and attitude, and breastfeeding practice during working hours. Results: From a total of 192 subjects, 73% of white-collar workers had good knowledge on breastfeeding, in contrast with SS% of blue-collar workers who had not good breastfeeding knowledge (P< 0.001). Most of the subjects were conducting breast pumping during working hours, however IS% of white-collar workers and 17% of blue-collar workers never breastfeed nor breast pumped at work. Working status (P= 0.005) and knowledge (P= 0.002) were factors associated with breastfeeding practice among workers. Conclusion: White-collar workers have a better knowledge, attitude, and practice toward breastfeeding. Knowledge improvement related to breastfeeding benefits and supports to working mothers are a key priority, however advocacy to employers, managers, and supervisors in providing breastfeeding facilitation and program support were also critical to successful breastfeeding practice among workers.