Purpose <p>The purpose of this study was to explore the interplay and influence of anxiety and depression between patients with low-risk localized prostate cancer on active surveillance (AS) and their close allies. The research sought to determine if emotional states are interdependent within these dyads, hypothesizing that both actor (self) and partner (close ally) effects would be significant.</p> Methods <p>This secondary analysis used data from a mixed-methods study involving patients and their close allies at Memorial Sloan Kettering Cancer Center. Participants completed the Memorial Anxiety Scale for Prostate Cancer (MAX-PC) and the Profile of Mood States (POMS) to assess anxiety and depression at baseline and 6 months. The Actor-Partner Interdependence Model (APIM) was employed to evaluate actor and partner effects for both outcomes.</p> Results <p>The study included 106 patients and their close allies, with 92% of patients being male and 82% of allies being spouses. Anxiety and depression scores at baseline were correlated between patients and allies (<i>r</i> = 0.40 and <i>r</i> = 0.29, respectively). However, APIM analysis revealed significant actor effects for anxiety and depression (<i>p</i> &lt; 0.05) but no partner effects, indicating that individuals’ baseline emotions influenced their own 6-month outcomes, without crossover influence from their partners.</p> Conclusions <p>While baseline anxiety and depression were related within patient-ally dyads, there was no evidence of interdependence over time. This suggests that individual emotional states are more predictive of future well-being than partner influence, highlighting the need for personalized psychological interventions during AS.</p>