The oxygen minimum zone (OMZ) in the Gulf of California entrance (GCE) is a crucial feature of the northeastern tropical Pacific, significantly influencing regional biogeochemical cycles and marine ecosystems. This study investigates the seasonal and interannual variability of the OMZ upper boundaries using a high-resolution physical-biogeochemical coupled model. The model results are evaluated against satellite observations, Argo profiles, and in situ data, demonstrating its capability to capture key dynamical processes, including mesoscale eddies, poleward undercurrents, and coastal-trapped waves (CTWs). The model reveals two alternating periods of shoaling and deepening of the OMZ boundary, modulated by the seasonal evolution of mesoscale dynamics and CTW propagation. El Niño Southern Oscillation (ENSO) events exert an evident influence, with El Niño causing a significant deepening and contraction of the OMZ, while La Niña leading to shoaling and expansion. The study highlights the complex interplay between local and remote oceanographic processes in determining the OMZ variability in the GCE. This research provides insights into the mechanisms driving OMZ dynamics in the Gulf of California and underscores the need for integrated observational and modeling approaches to predict the response of OMZs to ongoing climate variability.