No evidence from any longitudinal study design has been reported to date with regard to patient safety (PS) incidents witnessed by nursing students during their training. Therefore, with the aim of closing this gap in available knowledge, a longitudinal study was performed from 2012 to 2015 by involving all nursing students (n = 145) enrolled in two Italian nursing programs. At the end of each academic year, students were invited to report in writing all PS incidents witnessed during their clinical learning experience; the number of days each student spent in their clinical setting was also collected from administrative records. Ninety students were included and 94 incidents were reported: 17 (18.1%) by first year students, 27 (28.7%) by second year students, and 50 (53.2%) by third year students. One third of students did not report any PS incident at the end of each academic year, while only a few reported more than one. The incidence density was 3.8/1000 days of clinical training without statistical differences across academic years. Supporting nursing students by encouraging them to share, discuss, and reflect on their clinical learning experience might increase their confidence in reporting safety incidents.