Although educational experts recommend the use of formative assessment, there is a dearth of empirical studies on its impact on academic achievement. In this research the authors analyse to what extent participation and performance in formative assessment are associated with positive academic outcomes of pre-graduate students of health sciences. A total of 548 students from three health science degrees (Medicine, Psychology and Biology) from four Spanish universities were involved in this study. The students who carried out mid-term formative assessment got better marks and had higher success rates in final summative assessment that the students who did not participate. In addition, success in formative assessment tests was associated with better summative marks. Interestingly, participation in formative assessment was a better predictor of final outcome than success in formative assessment, a result that supports the key role of feedback in formative assessment. Students who took the mid-term examination, irrespective of their success, obtained feedback about their achievement and probably this determined their greater involvement in the learning process. Although causal relationships between formative and summative assessment cannot be established from this research, the generalized benefits of formative assessments found here encourage the practice of them in health sciences education.