The present study investigated professional designers’ practices in context, the role of their design tools and materials, the organization of their daily work and social connections related to their ongoing design projects. We examined the feasibility of using contextual event sampling as a method of studying professional design practices; this method involves repeated sampling of design events and actions in their social and cultural context. The data were collected electronically with Contextual Activity Sampling System (CASS), the rationale and usage of which are described in detail. The data analysis provided a view of the basic features of designers’ work; their activity, social interaction, and changes in location as well as the emotional dimensions of their experiences. Results indicated that designers’ work was multilayered, but they were not disturbed by the fluid and varying nature of the work and found satisfaction in it. We found the CASS- technology suitable for design research as it captures multimodal data and is applicable to variety of design interests and fields. Methodological implications regarding the contextual study of design practices and ideas of the tool development are discussed.