The present study longitudinally examined the effects of personality and social support on adjustment. Questionnaires were responded to over 4 periods of stay: just before arrival in Japan and three months, 9 months, and 21 months after arrival in Japan. Extraversion and neuroticism were measured in the 1st period; and needed, actual support, and adjustment in the 2nd, 3rd, and 4th periods. Thirty-three participants' completed data were analyzed. Three multiple regression analyses indicated that (a) needed support was a negative predictor and (b) actual support was a positive predictor of adjustment over all periods, while (c) extraversion was a positive predictor of the 4th period adjustment, and (d) there was no association between neuroticism and adjustment. The effects of support and personality on adjustment, which varied according to the period of stay, were discussed.