During the 2009–2010 A/H1N1 influenza pandemic, pregnant women infected with the virus experienced excess morbidity and mortality when compared with other groups. Once a vaccine was available, pregnant women were a priority group for vaccination. Only a few studies have reported on the uptake of 2009 A/H1N1 influenza vaccine among pregnant women during the pandemic and none were from Asia. The purpose of this study was to examine factors associated with 2009 A/H1N1 influenza vaccine uptake among pregnant women in Hong Kong. Using a multi-center, cross-sectional design, we recruited 549 postpartum women from four post-natal wards in Hong Kong over a 4-month period during the second wave of the A/H1N1 influenza pandemic in the winter and spring of 2010. Only 6.2% (n = 34) of participants had received the 2009 A/H1N1 influenza vaccine and 4.9% (n = 27) had received the seasonal influenza vaccine. The most common reasons for not receiving the 2009 A/H1N1 vaccine were fear of causing harm to themselves or their fetus. A high knowledge level (OR = 19.06; 95% CI 5.55, 65.48), more positive attitudes (OR = 3.52; 95% CI 1.37, 9.07), and having a family member who had the 2009 A/H1N1 influenza vaccine (OR = 7.69; 95% CI 2.92, 20.19) were independently and positively associated with vaccination. Study results show an unacceptably low uptake of the pandemic A/H1N1 influenza vaccine among pregnant women in Hong Kong. Interventions to increase influenza vaccine knowledge and uptake among this group should be a priority for future pandemic planning and seasonal vaccination campaigns.