The Central Coast of Vietnam, spanning from Thanh Hoa province to Binh Thuan province, holds a highly significant political and economic position, with the marine economy making substantial contributions to the existence and development of the region. This study aims to identify the factors influencing marine economic development (MED), evaluate the extent of influence of each factor, and determine whether security and coastal defense (SCD) plays an intermediary role in the development of the marine economy in the Central Coast provinces of Vietnam. The research conducted a typical survey of 268 fishermen engaged in marine economic activities, including aquaculture and the exploitation of aquatic resources, across the coastal provinces of the Central Coast of Vietnam. The collected data was analyzed using the structural equation modeling method through PLS-SEM software. The results of the study indicate that six factors have a direct and positive impact on MED. These factors, ranked by decreasing levels of influence, are: SCD (β = 0.412), Policy and Management (PM) (β = 0.329), Human Resources (HR) and Marine Infrastructure (MI) (both β = 0.268), Marine Resources (MR) (β = 0.204), and the lowest, Technology and Protection of Marine Environment (TPME) (β = 0.152). Additionally, the findings reveal that the three factors are HR, PM, and MI positively influence the SCD variable, with the levels of influence ranked as follows: HR (β = 0.272), PM (β = 0.224), and MI (β = 0.166). Moreover, at a significance level of 5%, all independent variables (HR, PM, and MI) exhibit statistically significant indirect relationships with MED through the SCD variable, confirming that SCD serves as an intermediary in the relationship with MED. Based on these findings, the study proposes managerial implications to support the development of the marine economy in the Central Coast provinces of Vietnam.