This study examined the determinants of micro, small, and medium enterprises (MSMEs) mortality and their implications for sustainability in Delta State, Nigeria. Specifically, it assessed the effect of access to finance, the relationship between managerial competence, and the influence of the regulatory environment on MSME sustainability. A mixed-method research design was adopted. The study employed purposive sampling across fifteen (15) Local Government Areas (LGAs), selecting two autonomous communities from each LGA, resulting in thirty (30) communities. From each community, five MSME owners and four managers were selected, yielding a total of 420 respondents for the quantitative component. Additionally, thirty (30) participants (one male and one female per LGA) were interviewed to support the qualitative analysis. Quantitative data were analysed using SPSS, with hypotheses tested through multiple regression analysis, while qualitative data were examined using thematic analysis. Findings revealed that access to finance was the strongest positive predictor of MSME sustainability (B = 0.595, p < 0.001). Managerial competence also showed a positive and significant effect (B = 0.236, p < 0.001). In contrast, the regulatory environment exhibited a negative and significant relationship with MSME sustainability (B = -0.187, p < 0.001), indicating that stringent regulations may hinder business survival. The study concludes that access to finance and managerial competence are critical drivers of MSME sustainability in Delta State, while an unfavourable regulatory environment poses significant challenges. It recommends the provision of targeted loan schemes, structured capacity-building programs for MSME operators, and the adoption of inclusive, consultative policy frameworks that involve MSME stakeholders in regulatory design. However, the generalizability of these findings beyond the study area remains subject to further empirical validation.