Introduction Longitudinal studies regarding educational strategies to help nursing students gain transcultural self-efficacy skills are limited. This study aimed to compare the long-term effects of an entry-level nursing culture course (ELNCC) on transcultural self-efficacy (TSE) in beginning nursing students with a graduating class who did not have the ELNCC. Method Using a longitudinal, quasi-experimental time-series design, data were collected using Jeffreys’s Transcultural Self-Efficacy Tool (TSET) from the experimental group ( n = 106) pre- and post-ELNCC, end of second semester, and program exit. A control group of 62 senior nursing students who did not take the ELNCC were administered the TSET once, at graduation. Results All posttest scores were significantly higher than pretest scores in overall TSE, cognitive, practical, and affective dimensions. At graduation, the experimental group’s scores were significantly higher than those of the control group in all dimensions except the affective. Discussion This study supports the early introduction of a separate culture course with field components to teach TSE to nursing students.