Abstract Personality effects on perceived support from social relationships and vice versa were longitudinally studied over adolescence. Within personality, core (Big Five personality traits) and surface characteristics (global self-worth, perceived peer acceptance, and loneliness) were distinguished. Core, but not surface, characteristics at age 12 predicted support from both parents and peers at age 17 after controlling for support at age 12. Support at age 12 predicted surface, but not core, characteristics at age 17 after controlling for personality at age 12. These findings are interpreted within a dual model of personality–relationship transaction. Core characteristics are relatively stable traits that are largely immune against experiences in relationships and continuously influence their flux and flow. Surface characteristics are more open to relationship influences, and are therefore less stable.