The Wnt/beta-catenin pathway is involved in cell functions governing development and disease. In modeling postentry restriction of human immunodeficiency virus (HIV) replication in astrocytes, we reported that part of this natural resistance to productive replication of HIV in astrocytes involved expression of proteins of the Wnt/beta-catenin signaling pathway. We determined here whether induction of beta-catenin signaling in peripheral blood mononuclear cells (PBMCs) can modulate HIV replication. Given that lithium is an inducer of beta-catenin signaling, we used it as a tool to determine the impact of beta-catenin signaling on HIV replication in PBMCs. We demonstrated that lithium inhibited the replication of T-tropic and primary isolates of HIV by >90% and did so in noncytotoxic/noncytostatic concentrations and in a beta-catenin-dependent manner. Specifically, inhibiting beta-catenin signaling by transfection of dominant-negative mutant constructs to either T-cell factor 4, the downstream effector of Wnt signaling, or beta-catenin, the central mediator of this pathway, abrogated the ability of lithium to inhibit HIV replication. Moreover, when Wnt/beta-catenin signaling was inhibited, the level of HIV replication was enhanced by fourfold. To confirm the in vivo relevance of the beta-catenin pathway in repressing HIV replication, we evaluated HIV-positive antiretroviral therapy-naive patients who were on lithium therapy. These patients demonstrated a reduction in viral load, which increased as the dose of lithium was reduced. Collectively, these data indicate that beta-catenin signaling is an intrinsic molecular pathway restricting HIV replication in PBMCs.