Social media adoption by firms has generally increased over time; however, little is known about why small firms do or do not use these digital technologies. Using a survey of 268 Swiss small and medium- sized enterprises (SMEs), this study identifies the determinants of social media adoption by SMEs. The descriptive results show that only 35% of SMEs adopt social media for business purposes. On the basis of technology acceptance theories at the individual level as well as qualitative research this study develops theory, hypotheses, and a measurement instrument on factors and mechanisms influencing the strategic application of social media in SMEs. In line with technology acceptance theories, the results show that SME executives are mainly influenced by the expectancy of low returns as well as high perceived risks to not adopt social media applications in their companies. In contrast, aspects of perceived ease of use of social media have no effect on their social media adoption. However, aspects of perceived ease of use require a closer analysis on more complex patterns in the context of social media adoption in SMEs. The implications for research on small business management, technology adoption, and social media marketing are discussed.