Background & Aims: Cancer is one of the significant health problems in this century. The suffering caused by cancer can decrease the patient's sense of self-efficacy and psychological well-being. However, cancer patients' psychological well-being and self-efficacy are considered two essential variables in motivating them to follow the prescribed treatment program and increase the probability of successful treatment response. Psychological well-being refers to a sense of health that includes full awareness of all aspects of the individual's integrity. Psychological well-being is a core feature of mental health. It may be defined as having hedonic (enjoyment, pleasure) and eudaimonic (meaning, fulfillment) happiness, as well as resilience (coping, emotion regulation, healthy problem solving). The Six-factor Model of Psychological Well-being is a theory developed by Ryff which determines six factors that contribute to an individual's psychological well-being, contentment, and happiness. Psychological well-being consists of positive relationships with others, personal mastery, autonomy, a feeling of purpose and meaning in life, and personal growth and development. Psychological well-being is attained by achieving a state of balance affected by both challenging and rewarding life events. People with high well-being experience mainly positive emotions and have a positive evaluation. Self-efficacy refers to the perception of one's ability to act according to one's desire. Self-efficacy reflects confidence in exerting control over one's motivation, behavior, and social environment. A strong sense of self-efficacy promotes human accomplishment and personal well-being. A person with high self-efficacy views challenges as things that are supposed to be mastered rather than threats to avoid. These people can recover from failure faster and are more likely to attribute failure to a lack of effort. They approach threatening situations with the belief that they can control them. These things have been linked to lower levels of stress and a lower vulnerability to depression. According to numerous studies, in cancer patients, interventions to increase the sense of self-efficacy facilitate the treatment process, increase the therapeutic response and reduce the disease's symptoms. Also, higher self-efficacy increases the adaptation of cancer patients to infection and improves the quality of life. Compassion-Focused Therapy has received a lot of attention recently. Compassion-focused therapy aims to help promote mental and emotional healing by encouraging people in treatment to be compassionate toward themselves and other people. Compassion-focused therapy was founded by Paul Gilbert (2000) in response to the observation that many people, particularly those high in shame and self-criticism, were experiencing difficulties generating kind and self-supporting inner voices when engaging in traditional therapy. It was observed that although these individuals were able to engage with cognitive and behavioral tasks, they still responded poorly to therapy. Self-compassion focus on kindness to oneself in the face of self-judgment, human commonalities in front of isolation, and mindfulness. Self-compassion is associated with positive emotions and the ability to hold negative emotions in a non-judgmental consciousness. Compassion, both toward the self and toward others, is an emotional response believed by many to be an essential aspect of well-being. Therefore, the present study seeks to answer whether compassion-focused Therapy is effective on psychological well-being and self-efficacy in people with cancer. Methods: The design of the present study was quasi-experimental with a pretest-posttest and control group. The necessary permission was first obtained from the ethics committee of Hormozgan University of Medical Sciences with the code IR to conduct this study. HUMS.REC.1398.306. This study's statistical population included all cancer patients referred to Shahid Fayyaz Bakhsh Hospital in Tehran in 1398, of which 34 people who met the inclusion criteria and were willing to participate in the study were purposefully selected and randomly assigned to experimental and control groups. The experimental group underwent eight sessions of 90-minute treatment focused on compassion in a group and weekly manner. Patients in both groups answered the research questionnaires at the beginning and immediately after the intervention. Inclusion criteria included: maximum age of 65, lowest literacy, at least six months after diagnosis, no severe mental disorder, and substance abuse. Exclusion criteria include the absence of more than two sessions in treatment, unwillingness to continue to participate in the study, and the occurrence of acute physical and mental disorders that do not allow continued participation in the sessions. At the end of the treatment sessions, two people from each group were excluded due to non-participation in the study, and finally, 15 people remained in each group. Generalized self-efficacy scale AND Ryff's psychological well-being scales were used to collect data. Results: Based on demographic information from the experimental and control groups, 15 cancer patients each participated; the mean age of the subjects in the experimental group was 38.12 years and in the control group was 36.94 years. The mean duration of the disease in the experimental group was 4.97, and in the control group was 5.33 years. Multivariate analysis of covariance was used to compare the differences between groups in psychological well-being subscales. The multivariate analysis of covariance showed a significant difference between the two groups in the linear composition of the dependent variables (Lambda Wickels = 0.03, F = 0.001, p < 0.001). Also, to compare the two groups in each of the components of psychological well-being as a dependent variable, the test of effects between subjects in the text of the univariate analysis of covariance test was used. The results showed that after controlling the effect of pre-tests on the post-test score, the group effect on the components of psychological well-being in the post-test has become significant. Univariate covariance analysis was used to compare the two groups in self-efficacy score and total psychological well-being score. The results showed that by controlling the pre-test scores, the group's effect on the self-efficacy post-test score and the total score of psychological well-being is significant. Conclusion: This study aimed to determine the effectiveness of compassion-focused Therapy on cancer patients' psychological well-being and self-efficacy. The results showed that compassion-focused Therapy could significantly positively affect cancer patients' psychological well-being and self-efficacy. Explaining these results, it should be noted that according to the compassionate view, people who have high self-judgment are more likely to blame themselves for stressful life events. The basic premise of compassion-focused Therapy is that not only are feelings of shame about brokenness and self-blame not helping to solve problems, but such a reproachful pattern can be the source of many mental disorders and poor well-being. In compassionate Therapy, by creating a new perspective, people who constantly criticize themselves are helped to achieve growth and development and choose the options they can. Also, in case of failure, instead of being unkind and judgmental towards themselves, they should appear with a state of compassion and acceptance towards themselves, which can gradually help to strengthen one's self-efficacy and psychological well-being. Some of the critical steps involved in compassion-focused therapy sessions are the use of imagery, compassionate thinking to the self and others, responding to self-criticism through self-compassion, and practicing human behavior, often complimented with letter or diary writing. Compassion-focused Therapy encourages the client to focus on, understand, and feel compassion to the self during negative thought processes, with a strong focus on nurturing compassion within the self. Compassion-focused Therapy helps the individual to accept problems and failures and illness and disability as part of shared human experiences by teaching the components of self-kindness, a shared sense of humanity, and mindfulness. [ABSTRACT FROM AUTHOR]