This study addresses the uncertainty surrounding the effectiveness of commercialized security services in preventing and mitigating terrorism in Nairobi County, Kenya, a concern heightened by past attacks on commercial malls. Focusing specifically on the effectiveness of these measures, the study employed a mixed-method, convergent parallel approach, with data collected from private security personnel, mall tenants, and visitors across 19 malls of varying sizes. The research was guided by the Routine Activities Theory and Situational Crime Prevention Theory. Quantitative data from the sample, comprising 12 security personnel, 34 tenants, 2 managers, and 344 visitors, were analyzed using descriptive statistics, Pearson correlation, and regression analysis. Qualitative data underwent thematic analysis. The findings reveal that, despite the implementation of commercialized security measures, their overall effectiveness in preventing terrorist threats reflects a nuanced state with room for improvement. While visitors generally hold positive perceptions of the security presence, indicating a baseline level of confidence, the study highlights notable variability in views among private security personnel regarding their strategies. This suggests that the impact of security measures is not uniformly perceived or experienced across different stakeholders. The results underscore the importance of targeted communication strategies and the need for more tailored, rather than one-size-fits-all, approaches to security management. The study recommends enhanced communication and specialized training for security personnel to foster a safer shopping environment and improve shopper confidence. Ultimately, the effectiveness of commercial security in malls against terrorism is influenced by a complex interplay of resource allocation, personnel training, and clear communication.