Tourism has emerged as a major industry worldwide and a sector in many countries. This sector has experienced a rapid growth and has become a key driver for sustainable socioeconomic developments globally. However, tourism is also a vector of environmental degradation through the emission of greenhouse gases (GHG). Therefore, the aim of this study was to analyze the main factors that are affecting the tourism demand in ASEAN-5 countries. Using a panel of five ASEAN countries over a 44-year period and applying the Pooled Mean Group (PMG) approach, the empirical results have shown that the major determinants of tourism demand in these countries are income, trade, tourism price, and carbon dioxide emission. The results have also shown that the PMG performed better than the Mean Group (MG) estimator. This paper refers to the PMG estimator because it constrains the long run coefficients to be identical, but allows the short run coefficients and error variances to differ across groups. Income and trade appeared to exert significant positive impacts on tourism demand, whereas tourism price and carbon dioxide emissions have negative impacts on tourism demand in these ASEAN-5 countries. The results would be a good reference for policy makers in these specific countries.