When attempting to communicate flood risk, trust in and perceptions toward risk-information disseminated as well as individual efficacy factors can play a significant role in affecting risk-mitigation motivation and intention. This study seeks to examine how risk communication, risk perception and efficacy factors affect evacuation motivation and behavioral intentions in response to a presumed flood risk, basing on a conceptual framework guided by protection motivation theory (PMT). An online survey was administered to college students (N = 239) from a region that is subject to sea level rise and storm surges. Path analysis results indicate that while less information-source trust predicts greater risk perception, greater information-source trust predicts greater mitigation information-seeking intention, lower self-efficacy and stronger response efficacy. As lower mitigation-information-seeking intention similarly predicts greater risk perception, greater mitigation information-seeking intention also predicts stronger response efficacy. Significant predictors of evacuation motivation include lower risk perception as well as greater information-source trust, severity perception and response efficacy. Implications of these findings are discussed in terms of information dissemination channels, messaging strategies, and recent severe flooding events.