Uncertainty around the real-time output gap has important implications for fiscal policy. This study uses successive vintages of the World Economic Outlook for emerging markets (EMs) during 1998-2022 to examine the reaction of discretionary fiscal policy to uncertain economic cycle in real-time. The findings show that EMs tend to have persistently negative and significantly more volatile real-time output gap estimates compared to advanced economies (AEs) and are less responsive to the output gap shocks. We calibrate a New Keynesian DSGE model to match the behavior of an average EM. The results from the model suggest that when EM policy makers are equally concerned about uncertainty around the output gap estimates and about fiscal implementation, fiscal policy is less counter-cyclical than the benchmark case with no uncertainty, entailing an efficiency loss for the purpose of output gap stabilization. On the other hand, when the concern is only about output gap uncertainty, EM policy makers tend to react more counter-cyclically but at a cost of public debt spiking in the short term and stabilizing over the long term. This implies that it might be optimal for EM policy makers to act more aggressively to stabilize the economy. We show that by adjusting the relative importance of output gap vs debt stabilization in their objective function, EM policy makers can achieve a similar outcome as in the benchmark case with no uncertainty.