Online social networks have become a popular channel through which individuals obtain opinions and evaluations that enable them to make informed decisions. Studies have determined that traditional media are a key factor influencing various markets. The present study explored the relationship between social media and housing market changes. The OpView database was searched to retrieve online responses posted between 2016 and 2020 on various social media platforms (i.e., Facebook and PTT). Social media sentiment indices, which were constructed on the basis of the collected online responses, were used to analyze the correlations of the responses with housing price, transaction volume, time-on-the-market, and price concessions. The results indicate that the general, positive, negative, and neutral online responses posted on Facebook and PTT significantly influenced both housing prices and transaction volume. However, only the online responses posted on PTT significantly affected time-on-the-market and price concessions. The results of a Granger causality test revealed the two-way causal relationships of housing prices and transaction volume with online responses, indicating the presence of a feedback mechanism. However, online responses only affected time-on-the-market in one direction, and their causal relationship with price concessions was weak. The results obtained using the impact response function indicate that the effect of Facebook online responses on housing prices was only significant and positive during the initial period of shock. By contrast, the positive and negative effects of PTT online responses on housing prices and price concessions, respectively, persisted for a longer period. We determined that online social media responses influenced the housing market. Through an analysis of social media sentiment, we obtained a clearer understanding of housing market fluctuations.