Multiple factors that influence the learning experience of nursing students while they are in clinical training have been identified, such as the clinical learning environment, the supervision provided by supervisors, and the level of cooperation with the nurse teacher. The objective was to examine whether the relationship between the clinical placement duration and overall satisfaction with clinical training is mediated by the supervisory relationship and learning environment. A secondary analysis was conducted using the data from a cross-sectional study conducted in 17 higher educational institutions in nine European countries with the Clinical Learning Environment, Supervision and Nurse Teacher scale (n = 1903 pre-registration nursing students). Satisfaction with the supervisor and a good learning environment mediated the relationship between clinical placement duration and overall satisfaction as perceived by the students. Nursing students with longer clinical placement durations were more satisfied with clinical training as a result of both their satisfaction with their supervisor and their perceptions of good learning environment. The optimal duration a nursing student should remain in the different practice settings is approximately 7 weeks.