Objectives To study the percentage of pregnant women who consumed omega-3 fatty acids in the course of pregnancy, and to assess their knowledge on the source and potential health benefits of these supplements. Method An anonymous self- administered questionnaire on the use and knowledge of omega-3 fatty acids was distributed to the pregnant women in the antenatal clinic in the United Christian Hospital, Hong Kong in May 2012. Result Two hundred Fifty-four questionnaires were received. Fourteen (10.9%) and fifteen (14.7%) women from the first and third trimester group reported the consumption of omega-3 fatty acids during current pregnancy respectively. The mean score of all the subjects on knowledge of omega-3 fatty acids was 7.87 out of 12. Women who were taking omega-3 supplements, who had completed tertiary education, with monthly income >HK$30,000 and who were Hong Kong residents had significantly better knowledge. About 80% of the subjects would like to have more information on the use of omega-3 fatty acids supplementation during pregnancy. Conclusion Although there is still lack of concrete evidence on the benefits of omega-3 fatty acids in pregnancy, there were 10–15% of pregnant women taking these supplements despite their fair knowledge. Further study is required to confirm the benefits of omega-3 fatty acids and better public education in this area is recommended. It would be most appreciated if medical professionals can provide more information on various nutritional supplements to pregnant women.