Research and clinical interest in self-compassion has grown due to its associations with physical and mental health benefits. Widely used measures of self-compassion have conceptual and psychometric limitations that warrant attention. The purpose of this project was to develop a new self-compassion measure, the Brief Self-Compassion Inventory (BSCI), and test its psychometric properties. We developed items for the BSCI based on theory, prior research, and expert and cancer patient feedback. The BSCI was then tested with adults diagnosed with breast, gastrointestinal, lung, or prostate cancer (N= 404). Confirmatory factor analysis suggested a unidimensional structure, and internal consistency reliability was excellent. Construct validity of the BSCI was established through its correlations with psychological variables hypothesized to be related to self-compassion, such as mindfulness, acceptance of cancer, and other coping strategies. Furthermore, measurement invariance testing of the BSCI indicated that it could be used across patients of varying genders, cancer types, and stages of illness. In conclusion, the 5-item BSCI was determined to be psychometrically sound and suitable for use with adults of varying genders, cancer types, and stages of disease. The measure warrants testing with other medical and nonclinical populations.