This longitudinal path assay tested Yakunina et al.’s (2012) partially mediated model of the relationship between the five multicultural personality factors (MPQ) measured at Time 1 and psychological adjustment measured at Time 2 in 120 U.S. students studying in Costa Rica for a semester. With the addition of other individual and social variables, this model was also tested as a predictor of students’ sociocultural adaptation. Individual (multicultural personality traits, openness to diversity, study abroad goals, language proficiency), social (homestay experience, amount of contact with co-nationals, amount of contact with locals), and structural factors (participation in structured group programs) were considered. Results for psychological adjustment mainly backed Yakunina et al.’s findings except for the relationship between openness to diversity and adjustment, raising the question of whether level of openness to diversity itself changes over the course of the study abroad experience. For sociocultural adjustment, a partially mediated model was the best fit, with social interaction with locals serving as a mediator of students’ MPQ level of open-mindedness and the quality of the homestay experience. Level of language ability at Time 1 was a direct predictor of this type of adjustment. Thus, the two types of adjustment have different predictors, with language proficiency and social interactions with locals being most important for sociocultural adjustment. Implications of the results for study abroad programs and future research are debated.