Designing usable products is important to provide a competitive edge through user satisfaction. A first step to establish or improve a usability process is to perform a process assessment. As this may be costly, an alternative for organizations seeking for lighter assessments, especially small organizations, may be self-assessments. They can be carried out by an organization on its own to assess the capability of its process. Although there are specific assessment methods to assess the usability process, none of them provides a self-assessment method considering the specific characteristics of small organizations. The objective of this research is to propose a method for self-assessing the capability of the usability process in small organizations. The method consists of a usability process reference model, a measurement framework, an assessment model, and a self-assessment process supported by an online tool. Based on systematic mapping studies on usability capability/maturity models and software process self-assessment methods, we identified the specific requirements of such a method. The UPCASE method was systematically developed using a multi-method approach based on the ISO/IEC TR 29110 and ISO/TR 18529 standard. The method has been applied and evaluated with respect to its reliability, usability, comprehensibility and internal consistency through a series of case studies. First results indicate that the method may be reliable. Feedback also indicates that the method is easy to use and understandable even for non-software process improvement experts. The UPCASE method is a first step to the self-assessment of the usability process in small organizations supporting the systematic establishment and improvement of the usability process contributing to the improvement of the usability of their software products.