The functionality of various sectors truly depends on how they implement what they are signatory to. In proffering an easy way out such a hook and hurdle, this study reviews the literature on the integration of ISO 14001 (Environmental Management Systems) and ISO 45001 (Occupational Health and Safety Management System) in Nigeria’s industrial sector to develop a maturity-oriented interpretation of why certification intent often exceeds operational integration. This study employed a scoping review approach, structured in line with the PRISMA-ScR framework. Being guided by the Population-Concept-Context (PCC) framework, the study focused on 43 well-screened studies that included literature covering integrated management systems (IMS), the alignment of environmental management systems, occupational health and safety, and Nigerian industrial or closely related African contexts. The results showed that the weak transition from fragmented compliance to integrated operational maturity is a key challenge in Nigeria, not merely the incompatibility of the standards. High costs, regulatory and documentation fragmentation, capability deficits, and uneven leadership continuity were common recurring barriers, whereas top management commitment, digital environmental health and safety traceability, Annex SL/the harmonized structure, and integrated audit and review systems were strong enablers of integration. The study concluded that the integration of these (ISO 14001–ISO 45001) management systems is strongest in governing but their functions is at its weakest in day-to-day operations. It also clarified how the emergence of ISO 14001:2026 strengthens the case for linking the environmental management system with workers’ health and safety in manufacturing settings. Hence, the study meticulously recommended a four-level Nigerian IMS maturity model: ad-hoc, fragmented, integrated, and excellent. The study also synthesized Nigeria-focused and Africa-relevant evidence on the integration of ISO 14001–ISO 45001 through the lens of operational maturity rather than certification prevalence.