Conservation planning has historically been restricted to planning within single realms (i.e., marine, terrestrial, or freshwater). Recently progress has been made in approaches for cross-realm planning which may enhance the ability to effectively manage processes that sustain biodiversity and ecosystem functions (e.g., connectivity) and thus minimize threats more efficiently. Current advances, however, have not optimally accounted for the fact that individual conservation management actions often have impacts across realms. We advance the existing cross-realm planning literature by presenting a conceptual framework for considering both co-benefits and tradeoffs between multiple realms (specifically freshwater and terrestrial). This conceptual framework is founded on a review of 1) the shared threats and management actions across realms and 2) existing literature on cross-realm planning to highlight recent research achievements and gaps. We identify current challenges and opportunities associated with the application of our framework and consider the more general prospects for cross-realm planning.