Cancer survivors report disruptions to their relationships, including decreased sex drive and fear of initiating sex with their partner. Although research indicates that sexual functioning is not directly related to subjective well-being, higher intimacy is positively associated with higher life satisfaction. Psychological flexibility, the ability to make practical, values-based choices among many competing options, is the measurable outcome of Acceptance and Commitment Therapy (ACT). Inflexible individuals tend to ruminate and hold grudges leading to relational strain. Although previous research indicates relationships between psychological flexibility, anxiety, and depression, little research connects the specific pillars of psychological flexibility (Openness to Experience, Behavioural Awareness, Valued Action) to these outcomes. Thus, we investigated the relationships between intimacy, psychological flexibility, and mental health. In this study, we examined: (1) the connections between intimacy and mental wellness (e.g., anxiety, depression) in cancer survivors and (2) which pillars of psychological flexibility are most closely related to intimacy in psychological outcomes of cancer. Participants who reported being in a relationship and had a previous cancer diagnosis were recruited to complete questionnaires measuring factors associated with sexual activity and intimacy, psychological flexibility, satisfaction with life, as well as symptoms of anxiety and depression. All components of intimacy (emotional, sexual, social, intellectual, recreational) were inversely correlated with depression and anxiety. Mediation analysis indicated that psychological flexibility was a significant mediator in the relationship between emotional intimacy, anxiety, and depression. This research adds to the body of research supporting acceptance and commitment therapy to improve intimacy and relationship satisfaction levels, focusing on the most salient components of this population.