Substance use disorder has become an epidemic in the young adult population across the United States, and these numbers rose during the COVID-19 pandemic. Psychotherapy incorporating equine interaction has emerged to show promise in the mental health community as a complementary form of therapy for this age group and offered a viable treatment option during the pandemic due to the outdoor nature of the treatment environment. However, research concerning its use within a residential treatment program was lacking. The objective of this study was to evaluate the efficacy of psychotherapy incorporating equine interaction in a residential treatment program during the COVID-19 pandemic for developing an emotionally safe environment for learning for young adults. Participants (ages 18–25 years) were those in a substance abuse residential treatment program utilizing psychotherapy incorporating equine interaction during the COVID-19 pandemic. Participants were involved in weekly equine therapy for 2–7 weeks. Participants were divided according to length of stay at the residential facility and participation level with equine interactive activities. Assessment of emotional safety and long-term memory development was performed at the beginning and end of the treatment program. The development of memories centered around equine information that was covered during the treatment program. Semantic memory was assessed using a self-reporting knowledge exam and procedural memory was assessed using a skill evaluation. Emotional safety was determined using a self-reporting survey instrument. Paired t-tests determined significant improvement in emotional safety (p = 0.02) and semantic (p = 0.01) and procedural (p = 0.00) memory for all participants by the end of the program. The one-way analysis of variance indicated length of stay and participation level were not significant indicators of emotional safety (length of stay: p = 0.91, participation level: p = 0.98) and semantic (length of stay: p = 0.09, participation level: p = 0.60) and procedural (length of stay: p = 0.25, participation level: p = 0.09) memory development. These results suggest psychotherapy incorporating equine interaction was an efficient complementary therapeutic intervention for developing emotional safety and encouraging learning in a young-adult residential addiction treatment program during the COVID-19 pandemic.