To improve uptake of influenza vaccine in pregnancy, it is important to understand the factors that predict prenatal vaccination. The aim of this study was to test the capability of the theory of planned behavior, augmented with information constructs, to predict and explain influenza vaccination uptake in a sample of 600 pregnant individuals in Canada. A baseline survey at the start of influenza season assessed beliefs, norms, perceived control, and information-seeking behavior related to influenza vaccination in pregnancy, as well as respondent demographics. A follow-up survey at the conclusion of influenza season assessed self-reported influenza vaccine uptake as well as infant vaccination intentions. Multivariable analysis indicated that attitudes toward influenza vaccination in pregnancy, subjective norms, information seeking, and past vaccination behavior predicted intentions to be vaccinated, and intentions predicted vaccine uptake. Neither perceived control nor demographics were significant predictors of intentions or vaccine uptake. These findings suggest that presumptive offering of vaccination in pregnancy by health care providers, as well as patient and public health educational interventions, may be effective in communicating norms and strengthening positive attitudes and intentions concerning influenza vaccination in pregnancy, resulting in higher vaccine coverage.