In this study, the effects of science, technology, engineering and mathematics (STEM) focused Arduino practical activities on problem-solving and entrepreneurship skills were analysed using qualitative and quantitative methods. Also, the contribution of these activities to teacher candidates and their effects on the learning-teaching process were discussed by evaluating their views. The study group consisted of 31 final-year teacher candidates studying in the science teaching department of a university in Turkey. The quantitative findings reveal that STEM-focused Arduino practical activities have a positive effect on improving the problem-solving and entrepreneurship skills of teacher candidates. Their opinions also support these results. The teacher candidates stated that the practical activities contribute to their professional development, support the development of 21st-century skills such as problem-solving and creativity and positively affect the learning-teaching process. As a result, STEM-focused Arduino practical activities are of significance in terms of adopting an interdisciplinary approach to education following the requirements of the century and developing problem-solving, entrepreneurial and productive individuals.