In recent years, both individuals and the healthcare sector have become more interested to measure and improve health and well-being by using different self-tracking 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 semi-structured 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.