Increasing bodies of evidence suggest that keeping secrets may be detrimental to well-being and adjustment, whereas confiding secrets may alleviate the detriments of secrecy and benefit well-being and adjustment. However, few studies have addressed the consequences of keeping and confiding secrets simultaneously, and even fewer have done so longitudinally. This article reports on a two-wave longitudinal survey study among 278 adolescents (aged 13-18 years) that examined the associations of keeping and confiding a specific secret with psychosocial adjustment. Results confirmed a hypothesized longitudinal contribution of keeping a secret all to oneself to psychosocial problems, including depressive mood, low self-concept clarity, low self-control, loneliness, and poor relationship quality. Furthermore, confiding versus continuing to keep a secret all to oneself was associated with decreased psychosocial problems after six months, whereas starting to keep a secret versus not doing so was associated with increased psychosocial problems. These results suggest that the keeping or confiding of secrets may affect adolescents' psychosocial well-being and adjustment. (Contains 1 footnote and 4 tables.)