Background: Cancer is a serious and life-threatening disease with negative effects on physical andrnpsychological well-being of patients. Depression and anxiety are the commonest co-morbiditiesrnthat adversely affects how people feel, the way they think and how they act and it is common amongrncancer patients. The impact of common mental disorder (CMDs) on cancer patients is not wellrnrecognized and managed in Ethiopia while there is a dearth of evidence on the effect ofrnPsychotherapy on depression, anxiety and treatment outcome among cancer patients. Interpersonalrnpsychotherapy is one therapy technique used to treat common mental disorders.rnObjectives:-To determine the Effect of Interpersonal Psychotherapy On treatment outcome amongrnBreast Cancer patients with a common mental disorder at Tikur Anbessa specialized teachingrnHospital (TASH), Addis Ababa, 2018/19.rnMethods: A parallel randomized control trial was employed on 124 breast cancer patients withrnCMD that are randomly selected from TASH oncology unit Out-patient department in weeks. Thenrnstudy participants was randomly assigned as Intervention group (n=62) and control group (n=62)rnrandomly in weeks and also single blinding was employed so as the outcome assessors are blindedrnof the belongingness of individuals to specific study group.To avoid information contaminationrnpatients were randomized in weeks.As an outcome measure we hypothesized treatment outcome asrnthe dependent variable and it was assessed using a 30 item questionnaire of quality of lifernmeasurement scale. Depression and anxiety were the independent variables that are measured withrnhospital anxiety and depression measurement scale. Both tools were validated for use inrnEthiopia.Psychotherapy was given for a month in a weekly basis. Then outcome was measured twornweeks after the final therapy with similar tool that were used at baseline.Data was analysed usingrnGLM (ANCOVA) to control the effect of confounders. With 95% confidence interval and P-valuern< 0.05 was used to declare the statistical significance. rnResult: Interpersonal Psychotherapy for Ethiopian use (IPT-E) had an effect on treatment outcome.rnIPT-E had a significant effect in decreasing anxiety, -5.76 with 95% CI (-7.10, -2.90) andrndepression, -4.74 with 95% (-6.44, -3.10) and with an IPT-E had also a significant effect on qualityrnof life domains of physical, role, cognitive, emotional and social functioning with (p