Middle East. Droughts are a major natural disaster in almost every region of the world, causing negative impacts on natural resources and water basin management. However, it is challenging to study drought mechanisms in transboundary rivers where hydrometeorological observations are often not available or limited due to administrative issues. This study aims to assess drought conditions at three Iraqi transboundary river basins – (a) Mosul River Basin (between Iraq and Turkey), (b) Qadisiyah River Basin (between Iraq, Syria and Turkey), and (c) Dukan River Basin (between Iraq and Iran). The Famine Early Warning Systems Network Land Data Assimilation System (FLDAS) and satellite datasets have been used to calculate various drought indices and reservoir areas for the study period between 1987 and 2019. We exhibited the usefulness of FLDAS and satellite datasets in analyzing the variations and trends in hydro-meteorological variables and reservoirs surface areas over three transboundary river basins. Results exposed a significant drought exacerbation over the study regions during the periods of 1989–1991, 2000–2003, 2007–2012, and 2015–2018. Based on our analysis on drought duration and severity for inside- and outside- Iraq, we suggest the long-term meteorological drought indices (12-,24-month timescales) in monitoring drought conditions. Our results could be beneficial for water and natural resources managers in understanding spatial variability and impact of droughts. •Evaluation of ten different drought indices•Understanding of drought conditions based on administrative boundary•Study on three transboundary river basins across different climactic conditions