Objective: To examine prostate cancer (PCa) survivors' sexual help-seeking intentions, behaviours, and unmet needs. Methods: In this prospective cohort study, men who underwent active, non-hormonal treatment completed baseline (N = 558) and 6-month follow-up (N = 387) questionnaires. Theory of planned behaviour (TPB) constructs (sexual help-seeking intention, perceived behavioural control (PBC), subjective norm, attitude), masculine values (e.g., sexual importance/priority, emotional self-reliance), sex life and functioning, sexual supportive care needs, distress (anxiety, depression), and sexual help-seeking behaviour were assessed. Results: Most men (M age = 64.6 years; M years post-diagnosis = 4.0) received prostatectomy (93%), reported severe erectile dysfunction (52%), ≥ 1 unmet sexual care need (66%), and sought help from a doctor (baseline 52%, follow-up 42%). Sexual care needs were significantly associated with poorer erectile function, reduced satisfaction with sex-life, valuing sex as important/integral to identity (masculine values), and increased depression (p ≤ 0.001). Sexual help-seeking intentions were significantly associated with valuing sex as important/integral to identity, recent help-seeking, greater confidence/control, perceiving support from important others, and positive attitudes, for sexual help-seeking (p < 0.001). Significant predictors of sexual help-seeking (follow-up) were baseline intentions, recent help-seeking (p < 0.001), and increased anxiety (p < 0.05). Conclusions: Men's unmet sexual care needs, sexual help-seeking intentions, and behaviour appear driven by the importance/value attributed to sex, distress, positive feelings, support from others, and confidence for help-seeking. Psychosocial providers are well-placed to address men's concerns, yet few sought their assistance. Interventions to improve men's access to effective sexual care are needed, particularly focused on reframing masculine values about the importance of sex and leveraging TPB-based predictors of help-seeking.