While forgivingness has been associated with health and psychosocial variables, previous cross-sectional studies could not address the temporal characteristics of their relationships. To overcome this limitation, the present study investigated longitudinally the antecedents and consequences of forgivingness, as well as the association of mood states and Big Five personality traits with forgivingness. We obtained complete data on forgivingness, Big Five personality traits, and moods across three waves of surveys over six years from 294 participants, and from more participants who completed only one or two waves. Structural equation modelling for the cross-lagged longitudinal analysis was applied, controlling for auto-correlations and effects of external variables. Our data revealed a weak link from conscientiousness to later forgivingness. More importantly, forgivingness predicted emotional stability, agreeableness and less negative moods longitudinally. Our findings challenged the previously-assumed causative roles of Big Five personality traits in forgivingness but corroborated the desirable predictive effects of being forgiving in developing more positive moods and personality characteristics.