This study analyzes the effect on levels of patient anxiety and depression of a partner joining a cardiac rehabilitation program support group, also taking into account the sex of the patient. The study was undertaken using a two-group comparison design with pre-and post-test measures in non-equivalent groups. The sample comprised patients in the cardiac rehabilitation program (CRP) at the Ramón y Cajal Hospital, Madrid (Spain). Analysis of covariance (ANCOVA) showed direct effects of sex and partner participation in support groups on the anxiety trait. Similarly, interaction effects were observed between the sex variable and partner participation. These results indicate the pertinence of designing separate groups for patients and partners.