Homesickness is common among university students and associated with mental health problems. Most previous studies assessed homesickness as a summary of the past weeks. However, there may be significant fluctuations across situations. At the current residence, homesickness may especially be triggered during (phone) interactions with attachment figures. Dutch and international 1st-year students (n = 92) completed the Utrecht Homesickness Scale and subsequently used a smartphone application to record social interactions for 14 days (ecological momentary assessment [EMA]). For each interaction they reported the social context (e.g. location, contact type) and their affective state, including homesickness. Homesickness in the past weeks and momentary homesickness were both higher in international students than in Dutch students. Feeling homesick was highest at participants' current residency, when interacting with parents, or when using video-chat. When participants felt more homesick, they reported less pleasant and more unpleasant affect. In conclusion, EMA provided insight in cross-situational variations in homesickness.