The aim of this study was to determine whether an individual's defense style significantly influences his or her relationship satisfaction in the transition to parenthood. Questionnaire measures of relationship satisfaction and personality (including defense style) were administered in the midtrimester of pregnancy to 157 couples expecting their first child. Follow-up assessments of relationship satisfaction were conducted at 4 and 12 months postpartum. The strongest predictor of current relationship satisfaction for both mothers and fathers was prior relationship satisfaction. In addition, measures of defense style were found to contribute significantly to the prediction of relationship satisfaction at both postpartum assessments. The results support the usefulness of models of defense style for understanding processes of coping and adjustment in normal adults. Methodological issues in the measurement of defense style and gender differences in defense functioning are discussed.