Objective 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 to 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 2012 to February 2013. Subjects were female workers whose children aged 6 months to 24 years 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 55% of blue-collar workers who had not good of breastfeeding knowledge (P