Mycobacterium avium complex (MAC) organisms are widespread environmental pathogens associated with chronic pulmonary infections. Although M. avium is known to invade epithelial cells, the molecular mechanisms underlying this process remain incompletely understood. In this study, we identified a novel role for MAVRS09815 (formerly MAV2054), a family 2A encapsulin nanocompartment shell protein, in mediating bacterial adhesion, epithelial cell invasion, and in vivo virulence. We engineered a recombinant M. smegmatis strain expressing MAV2054 (Ms_2054) and an M. avium MAV2054 deletion mutant (Δ2054). Ms_2054 exhibited enhanced epithelial invasion, whereas Δ2054 showed reduced intracellular survival. Recombinant MAV2054 protein was bound directly to human epithelial cells in a dose-dependent manner. Pretreatment of host cells with cytochalasin D or vinblastine significantly inhibited bacterial internalization, indicating that MAV2054-mediated invasion is cytoskeleton-dependent. Confocal and scanning electron microscopy revealed MAV2054-dependent membrane rearrangements during infection. Pull-down assays demonstrated that MAV2054 activates Cdc42, a key regulator of actin polymerization, with reduced activation observed in Δ2054-infected cells. In a murine intratracheal infection model, the Δ2054 exhibited significantly reduced bacterial burdens and lung inflammation compared to the wild type. These findings demonstrate that MAV2054 enhances M. avium virulence by promoting epithelial cell invasion through Cdc42-dependent cytoskeletal remodeling. This study reveals a previously unrecognized role for an encapsulin-like protein in host-pathogen interactions and highlights its potential as a therapeutic target in MAC infections.