Dynamic security is an important factor in survivability of all-electric ships. On the other hand, region-based security assessment methods are efficient for online applications. In this paper, a deterministic method is presented to assess Dynamic Secure Region (DSR) in all-electric ships. In this method, MATLAB and DSATools™, a dynamic security assessment software package, are linked together to assess security of a wide range of ship working points and determine the dynamically secure operating region. To illustrate how this approach works, it was used to assess the DSR of a notional all-electric ship model. In this study, about 6,000 working points were simulated for 58 contingencies and their security was assessed regarding 4 security criteria. The results showed that a probabilistic security assessment method may be more effective for such a power system.