Brittle materials are widely used for producing important components in the industry of optics, optoelectronics, and semiconductors. Ultraprecision machining of brittle materials with high surface quality and surface integrity helps improve the functional performance and lifespan of the components. According to their hardness, brittle materials can be roughly divided into hard-brittle and soft-brittle. Although there have been some literature reviews for ultraprecision machining of hard-brittle materials, up to date, very few review papers are available that focus on the processing of soft-brittle materials. Due to the ‘soft’ and ‘brittle’ properties, this group of materials has unique machining characteristics. This paper presents a comprehensive overview of recent advances in ultraprecision machining of soft-brittle materials. Critical aspects of machining mechanisms, such as chip formation, surface topography, and subsurface damage for different machining methods, including diamond turning, micro end milling, ultraprecision grinding, and micro/nano burnishing, are compared in terms of tool-workpiece interaction. The effects of tool geometries on the machining characteristics of soft-brittle materials are systematically analyzed, and dominating factors are sorted out. Problems and challenges in the engineering applications are identified, and solutions/guidelines for future R&D are provided.