Climate change has made many alterations to the Earth's climate, including hydro-climatic extreme events. For investigating the effect of climate change on hydro-meteorological droughts in the Kamal-Saleh dam basin in Markazi province, Iran, a new and comprehensive index was developed for accurate estimation of drought in a more realistic condition, for future climate conditions. This aggregate drought index (ADI) represents the main characteristics of meteorological and hydrological drought. Temperature and precipitation projections for future climates were simulated by five CMIP5 models and downscaled over the study area for the periods of 2050s (2040-2069) and 2080s (2070-2099) relative to the baseline period (1976-2005). By fitting five univariate distribution functions on drought severity and duration, proper marginal distributions were selected. The joint distribution of drought severity and duration was chosen from five types of copula functions. The results revealed that severe droughts are expected to occur frequently in a shorter period in the future.