Social media word of mouth (WOM) involves much interaction and engagement between users in their own networks. The feature of reposting on social media allows WOM to spread fast and easily. Original posts or reposts can be easily identified, perceived, and processed by social media users for purchase decisions. Then, we propose to investigate social media WOM post diversity, which reflects the variation of posts. Further, we propose that the relationship between social media WOM post diversity and sales can be conditional on the three previously established dimensions: volume, valence, and variance. The findings, reflecting approximately 1.5 million posts about 51 movies on a social media site, suggest that WOM post diversity, as measured by post entropy, positively associates with movie sales, contingent on low WOM volume, high valence, and high variance.