Happiness is of great importance in mental health and in dealing with the problems of today`s world. Identifying the factors affecting the happiness is the main topic of positive psychology because this component, similar to a shield, can protect humans against stress and improve the immune system against some diseases such as cancer. Therefore, this study aims to determine the level of happiness and factors affecting it in patients diagnosed with breast cancer. A descriptive-correlational study was performed. A total of 50 breast cancer patients, referring to Neshat Park Day Clinic, Kerman, Iran, were enrolled using convenience sampling method and ensuring to meet the inclusion criteria. Data were collected using Demographic Questionnaire and Oxford Happiness Questionnaire (OHQ). Stata vesion11 was employed to analyze the data. Findings show that the happiness score is 37.68 in breast cancer patients, showing a medium level of happiness. The results also show that happiness has no significant relationship with all demographic characteristics including age, marital status, level of education, insurance, employment status, monthly income, history of other diseases, duration of breast cancer, the duration of treatment, development of breast cancer among another family member, and breast cancer-related training (P>0.05). Different individual characteristics of breast cancer patients have no impact on their happiness. The impact resulting from cancer is likely to be more effective in patients` mental status. Conducting the study is recommended among more patients.
