In line with global conservation targets, Iran aims to increase its protected area coverage from c. 11% to 20%. We explored an area-efficient and balanced set of criteria to find areas that best complement existing protected areas for achieving these targets. We used distribution maps of all threatened vertebrates in a systematic conservation planning approach and compared four different methods of weighting species and locations: 1) species weighted equally, 2) weighted by distribution characteristics (i.e. presence, origin, seasonality) and important habitat surrogates (Important Bird Areas and Endemic Bird Areas), 3) species’ level of endemism, and IUCN Red List threat status, and 4) considering opportunity cost based on levels of urbanization to reflect the current land’s ecological conditions. We then determined the extent to which existing protected areas cover conservation priorities for different species groups, and explored how new priorities complement Iran’s protected area network to achieve national target to protect 20% of its land area. Our findings showed that parts of terrestrial ecoregions in the north, north-west and west of the country were consistently important in all scenarios, representing the best places to start increasing protected area coverage. Protecting 20% of the country in the prioritizations constrained by existing protected areas would conserve biodiversity groups in 70% to 100% of their original distribution, except for birds and mammals for which the protection coverage was lower. Our study locates the important areas for conservation in line with national and international targets that require effective conservation action.

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