Introduction: Antenatal exercises provide many health benefits not only to pregnant mothers but also to the fetuses. Adequate knowledge among pregnant mothers is vital to promote practicing of it. The aim of this study was to describe the knowledge, attitudes and practices regarding antenatal exercises and factors associated with them among pregnant women attending De Soyza Maternity Hospital (DMH) Colombo. Methods: A descriptive cross-sectional study was conducted among 110 pregnant mothers with a period of amenorrhoea of 20 weeks or more using an interviewer-administered questionnaire. Results: Knowledge regarding antenatal exercises was ‘poor’ among a majority (72.7%, n=80). Only 6.4% (n=7) and 5.5% (n=6) knew the importance of pelvic floor strengthening exercises and its technique, respectively. Most had somewhat favourable (49.1%, n=54) and favourable (35.5%, n=39) attitudes towards antenatal exercises while overall practices were ‘poor’ with a majority not exercising (86.4%, n=95). The sources of information were written media (49.1%, n =54) and electronic media (48.2%, n=53). Doing a job during pregnancy was significantly associated with possessing a ‘Good/Excellent’ level of knowledge (p=0.02) while living in a district other than Colombo was also associated significantly with a ‘Good/Excellent’ level of knowledge (p=0.039) and a ‘Good’ level of practice (p=0.042). Average family monthly income of > Rs. 25000 was associated with a level of ‘Favorable’ attitude (p=0.004). Conclusion: Knowledge and practices regarding antenatal exercises among pregnant women attending DMH were suboptimal while their attitudes were mostly favourable. Measures should be taken to improve knowledge and practices of antenatal exercises during pregnancy