Since November 2012, Dutch civil defense organizations employ NL-Alert, a cellular broadcast-based warning system to inform the public. Individuals receive a message on their mobile phone about the actual threat, as well as some advice how to deal with the situation at hand. This study reports on the behavioral effects of NL-Alert (n = 643). The current risk communication literature suggested underlying mechanisms as perceived threat, efficacy beliefs, social norms, information sufficiency, and perceived message quality. Results indicate that adaptive behavior and behavioral avoidance can be predicted by subsets of these determinants. Affective and social predictors appear to be more important in this context that socio-cognitive predictors. Implications for the use of cellular broadcast systems like NL-Alert as a warning tool in emergency situations are discussed.