Despite rigorous regulatory frameworks like EASA Part-145 and FAA AC 120-79A, aviation maintenance organizations (AMOs) exhibit significant variance in safety compliance outcomes. This study investigates the influence of organisational culture on safety compliance behaviour among aviation maintenance technicians in Nigeria, addressing the gap between structural Safety Management Systems (SMS) and actual technician behaviour. Grounded in Edgar Schein’s tripartite model of organizational culture, the research employs a concurrent mixed-methods design, surveying 178 licensed and unlicensed technicians across various maintenance domains and conducting 20 semi-structured interviews. Quantitative results indicate that cultural dimensions explain 34% of the variance in routine compliance and 41% in discretionary safety behaviour. Management Commitment emerged as the strongest predictor of routine compliance (β = .29), while Just Culture was the dominant predictor of discretionary safety behaviour (β = .34). Notably, the effect of management commitment on discretionary behaviour was fully mediated by just culture perceptions. Production pressure negatively impacted both compliance types, disproportionately suppressing voluntary safety contributions. Qualitative findings revealed a dissonance between espoused safety values and underlying assumptions, with technicians describing SMS documentation as “audit theatre” and adhering to informal “real procedures” transmitted through peer enculturation. Core assumptions such as “experience trumps documentation” and “real professionals solve problems silently” were identified as primary drivers of non-compliance. The study concludes that sustainable safety compliance requires targeting basic underlying assumptions rather than merely enhancing artifacts or espoused values. Recommendations include establishing facilitated dialogue sessions to surface assumptions, implementing formal decision documentation protocols for safety-production trade-offs, and restructuring apprenticeship programs to integrate tacit knowledge formally. These findings offer AMO leaders and regulators evidence-based strategies for evolving from document-based auditing to performance-based cultural assessment.