What happens to their friendships when someone moves into a completely new social environment? Moving away from home to attend university is the first major life transition for many, and we studied friendship development in two incoming college cohorts. Using cohort network analysis, we investigated the impact of homophily in a broad range of traits for initial, short-term, and long-term friendship choice. Results revealed that homophily-driven self-segregation occurred within one term for two-thirds of the 16 traits analysed. There was little change once the initial networks had been established, indicating strong selection for homophily at the outset. Since, in a more mobile workforce, major transitions of this kind are now more common, there is a need for further work on these rapid social developments. This may be especially important in contexts where new members of a community (e.g. a business) need to be embedded quickly and where failure to do so can quickly result in loneliness.