Limited research examines women's beliefs about the value of exercise and their actual exercise behaviors during pregnancy and postpartum. A retrospective study of 74 postpartum women was conducted to examine women's behavioral, normative, and control beliefs about exercising during pregnancy and postpartum and to determine their most salient beliefs. In addition, women's prepregnancy, pregnancy, and postpartum exercise behavior was examined. We found that 1) the most common exercise beliefs during pregnancy were that exercise improves mood and physical limitations (e.g., nausea) obstructed exercise participation; 2) the most common exercise beliefs during postpartum were that exercise controls weight gain and a lack of time obstructed exercise participation; 3) women's husband/partner and family members most strongly influenced their pregnancy and postpartum exercise behavior; and 4) women exercised more before they were pregnant than during pregnancy and postpartum. Researchers and health care professionals are encouraged to examine and understand women's beliefs about exercising during their pregnancy and postpartum and design their interventions accordingly, in an attempt to increase women's exercise behavior during their childbearing years.