Background International Service Learning Trips (ISLT) provide health professional students the opportunity to provide healthcare, under the direction of trained faculty, to underserved populations in developing countries. Despite recent increases in international service learning trips, there is scant literature addressing concerns students have prior to attending such trips. This study focuses on identifying concerns before and after attending an ISLT and their impact on students. Methods A survey comprised of closed and open-ended questions was developed to elucidate student concerns prior to attending an ISLT and experiences which might influence concerns. A five-point Likert-scale (extremely concerned = 1, minimally concerned = 5) was used to rate apprehension and satisfaction. Paired t-test was used to compare pre- and post-trip concerns; Chi-Square test was used to compare groups. Results Thirty-five students (27 medical, 8 pharmacy) attended ISLTs in December 2013. All completed pre and post-trip surveys. Significant decreases were seen in concerns related to cultural barriers (4.14 vs 4.46, P = .047), disease/epidemics (3.34 vs 4.60, P < .001), natural disasters (3.94 vs 4.94, P < .001), terrorism (4.34 vs 4.94, P < .001), travel (3.86 vs 4.51, P < .001) monetary issues (3.80 vs 4.60, P < .001), hospitality (3.94 vs 4.74, P = .001) and food (3.83 vs 4.60, P < .001). Language and group dynamics remained concerns post-trip. On open-ended questions, students described benefits of attending an ISLT. Conclusions Students had multiple concerns prior to attending an ISLT. Most decreased upon return. Addressing concerns has the potential to decrease student apprehension. The results of this study highlight the benefits of providing ISLTs and supporting development of a curriculum incorporating trip-related concerns. Electronic supplementary material The online version of this article (doi:10.1186/s12909-015-0519-7) contains supplementary material, which is available to authorized users.