PurposeThe purpose of this article is to investigate the relationship between cash flow uncertainty and the underpricing of real estate investment trust (REIT) initial public offerings (IPOs) using hand-collected data on income guarantee in Thailand from January 2005 to December 2019.Design/methodology/approachThis article uses linear regression to determine the relationship between underpricing (initial return) and proxy for cash flow uncertainty (income guarantee), controlling for other factors. Because issuers can use several actions to signal their quality under asymmetric information, the joint decisions are analyzed as simultaneous equations and estimated using three-stage least square (3SLS) to address potential endogeneity concern.FindingsThis article finds that underpricing, on average, is negatively related to income guarantee, which is a proxy for ex ante cash flow uncertainty. The relationship is economically and statistically significant and robust to simultaneous equations estimation. Further investigation shows that REITs with income guarantee tend to have lower systematic risk (measured by CAPM beta) and returns, making the nature of some REITs more debt-like than equity-like.Practical implicationsFor issuers, the result suggests that offering income guarantee (which is more costly for assets with lower quality) can be a useful signal of asset quality to investors and reduce IPO discount. For institutional and retail investors, the results are informative about the risk-return tradeoffs in REIT IPO investment opportunities. Income guarantees makes REIT exposure more fix income-like, so there is a need to consider the credibility of the guarantor as well.Originality/valueThis article is the first to use income guarantee as an ex ante measure of cash flow uncertainty and explicitly investigates its linkage to IPO underpricing. This aspect of uncertainty and IPO underpricing remains little-studied in the academic literature. It also contributes to the growing literature of REIT IPOs in Asia.