This study’s aims were to evaluate the effects of Sorensen’s Therapy of Instability in Mood (Sorensen, 2005; Sorensen, Done & Rhodes, 2007), an intervention based on a short relapse-prevention program for clients suffering from Bipolar Disorder (BD), delivered within a clinical setting, by an assistant psychologist with limited training in CBT. The experimental treatment consisted of four individual sessions in addition to treatment as usual. Twelve clients with diagnoses of BD participated. Outcomes were measured across four domains: symptom severity, perceived hopelessness, perceived control over symptoms and level of insight. Measures of client satisfaction were also collected. Statistical analysis of the data revealed significant improvements to depression and perceived control levels at both one and three month follow-ups. In addition, clients reported significantly lower levels of hopelessness at three months follow-up. The study also considered the clinical significance of the research findings with the Jacobson-Truax (Jacobson & Truax, 1991) method. A substantial number of clients attained clinically significant changes with regards to depression, hopelessness and perceived control at one and three months follow-ups. Recovery rates at three months were 50%, 41.6% and 25% respectively. Neither statistically nor clinically significant changes were found with regards to mania or insight at either one or three month follow-ups. All clients reported high levels of satisfaction.