This article investigates the state of open innovation in Slovenia, using qualitative and quantitative research. Based on in-depth interviews with domestic and foreign experts in the field of open innovation, we identify the main advantages and reasons open innovation should be introduced in Slovenian companies, the main barriers that companies can encounter in the implementation of open innovation and suggestions for the successful development and implementation of the concept among Slovenian companies. A quantitative analysis of Slovenian companies shows that differences exist in implementing open innovation dimensions among micro, small, medium and large firms, as well as between manufacturing and service companies. We conclude by suggesting the steps to be taken to stimulate the development and implementation of open innovation in Slovenian companies, the implications for managers and policy-makers, as well as the limitations of our study, and future research.