This study aims to describe the effectiveness of external communication on the Regional Disaster Management Agency at Padang city (BPBD) in Implementing of Tsunami Early Warning System. The organization external communication’s problem in implementing tsunami early warning system became the background of the study. The lack of public understanding about tsunami early warning, unorderly in the evacuation, the reluctance in using the shelter as the evacuate place and the decreases number and quality of communication media in implementing tsunami early warning system by BPBD. This descriptive research is using a quantitative method in which the population is the people residing in the tsunami hazard zone area. The sample, the cluster random sampling technique is used. The data were collected using a questionnaire and measure with Likert scale and supported by documentation study. The results showed that the effectiveness of external communication on Regional Disaster Management Agency of Padang City in implementing the tsunami early warning system is quite useful. The efficiency of 65.48 is in the range of 60-79.99. There are two ineffective factors. First, the community action (taken from effective communication’s indicator) showed the value is 59 which means the sign is in the range 40-59.9 9. The second is from affect factors of the effective communication with value 59.66 means the indicator is in the range 40-59.9 9. Show More