Vietnam is one of the countries most affected by climate change. Therefore, communication activities on climate change in Vietnam are focused with various media such as television, newspapers, radio, internet etc. In particular, Facebook social network is a potential media but less interested and developed. In this topic, Audience Insight tool of the Facebook social network and the online sociological survey method were conducted to assess the current status and effectiveness of climate change communication activities via Facebook in Vietnam today. Vietnam ranks seventh in the world with 58 million users. However, the number of climate change communication fanpages has only about 15 fanpages with the largest number of followings is 94,721 persons. Among of the 10 most contented Facebook users in Vietnam today, there is no fanpage related to climate change. The results of research and evaluation two fanpages of climate change communication that are the most and most frequent followers in Vietnam showed that climate change communication via Facebook in Vietnam is not as effective as expected. At the same time, online survey results also pointed out the causes of the above problems. This is the scientific basis for management agencies to find the solutions to promote the strength of Facebook social network in climate change communication in the future.