We investigated how concealment and disclosure of secrets, two related but distinct processes, unfolded over the course of open-ended therapy for 39 clients and 9 therapists, using hierarchical linear modeling to identify longitudinal patterns and investigate relationships with working alliance and session quality. Results indicated that over the course of therapy, 85% of clients disclosed at least one secret and 41% concealed at least one secret, with 18% of sessions including a disclosure and 4% of sessions including concealment. Over time, clients were less likely to disclose secrets, and the secrets they chose to conceal were rated as less significant. Clients rated the working alliance lower after sessions when they disclosed secrets versus when they did not disclose, although the working alliance was not rated as poorly when the disclosed secrets were viewed as significant. Clients rated session quality higher after sessions when they disclosed secrets versus when they did not disclose, particularly when they disclosed preoccupying secrets. Clients tended to feel neutral or positive about their disclosures. Implications for practice and research are discussed. (PsycINFO Database Record (c) 2019 APA, all rights reserved)