This intervention study evaluates a decision-making aid for parents considering childhood immunizations. Participants (women in 3rd trimester of pregnancy, n = 100) rated likelihood of immunizing their child, anxiety, and perceptions of risk of the diseases and immunizations. Individuals were allocated to intervention group (received a decision aid) or control group (received standard care). Ratings were then repeated, and further ratings were obtained when the infant was 10 weeks old. The intervention compared with the comparison condition was associated with significant increase in likelihood of immunizing the infant on time, decreased perceptions of risks of immunizations, increased perceptions of risk of the diseases, reduced anxiety, and increased satisfaction. This intervention may form a useful basis for decision aids in health care settings.