Previous research on the determinants of homesickness has tended to produce inconsistent results and relied mostly on cross-sectional assessments. To capture the longitudinal perspective, we conducted a smartphone appbased study, monitoring the emergence and volatility of homesickness in international university exchange students (n = 148). Applying an experience sampling method (ESM), homesickness was measured every second day over a period of 3 months followed by a post hoc questionnaire to assess potential moderators. Multilevel modeling revealed that whereas age, Extraversion, Conscientiousness, Openness to Experience, voluntariness, previous stays abroad, support from host university, geographical distance, co-and host national identification, language proficiency, and pre-data collection duration of stay did not yield any effects, being male, scoring high on Neuroticism as well as Agreeableness, having difficulties in sociocultural adaptation, and being at the beginning of the stay (as opposed to later on) were related