Anthropogenic carbon dioxide emissions have been increasing rapidly in recent years, driving pH and oxygen levels to record low concentrations in the oceans. Eastern boundary upwelling systems such as the California Current experience exacerbated ocean acidification and hypoxia (OAH) due to the physical and chemical properties of the transported deeper waters. Research efforts have significantly increased in recent years to investigate the deleterious effects of climate change on marine species, but have not focused on the impacts of simultaneous environmental stressors. Additionally, few have explored the physiological impacts of these environmental stressors on early life stages, which are more vulnerable and represent natural population bottlenecks in organismal life cycles. The physiological response of the red sea urchin (Mesocentrotus franciscanus) to co-occurring stressors was assessed by exposing larvae to varying OAH conditions observed along the California coast. Graded responses, proportional to treatment severity, indicate that minor shifts in OAH affect morphology and gene expression, especially related to growth and pH homeostasis. In addition to this gradient, breakpoints can be detected, representing drastic shifts in response curves and a potential environmental threshold below which growth and performance are profoundly impacted. The phenotypic and transcriptional breakpoints occurred between DO of 2.64-3.67 mg/L and pH 7.6-7.85 with an additional transcriptional breakpoint between DO 0.88-1.54 mg/L and pH 7.2-7.45. By assessing the physiological response and gene expression of these species, we can inform future management actions to mitigate OAH-related impacts and maintain fishery populations.