In recent years, both individuals and the healthcare sector have become more interested to measure and improve health and well-being by using different selftracking technologies. However, the number of studies concerning the experiences that people have with these technologies is still rather limited. This study investigates the expectations and perceived short-term effects of using self-tracking technologies on users’ well-being. The focus is on the first weeks of usage i.e., the implementation phase. The study is qualitative in nature and based on thematic analysis of ten semistructured interviews. The results reveal that the perceived well-being effects of using a self-tracking technology are relatively minor during the implementation phase and in line with the expectations. The increase in well-being is expected to occur in a longer time scale. Perceived psychological well-being is found to be affected the most during the implementation phase. The results also reveal interesting findings regarding the use of self-tracking technologies. The results are discussed and several important implications are drawn.