Anticipatory Action (AA), the delivery of humanitarian assistance before a predictable shock, aims to mitigate the human and economic costs of climate-related crises before hazards reach their peaks. As governments and humanitarian actors expand the use of forecast-based triggers, pre-arranged financing, and context- and state-specific intervention packages, there is growing demand for evidence on the impacts of AA. This review synthesizes findings from 14 experimental and quasi-experimental impact evaluations conducted between 2010 and 2025, covering nine contexts, and across cold waves, cyclones, droughts, and floods. We find that AA generally performs better than post-shock response or no assistance. AA improves food security, reduces negative coping strategies, and increases household pre-emptive actions, although impacts vary across measures, hazards, and interventions. Positive impacts found are concentrated during and immediately after the shock, consistent with the intention of AA. The evidence base is young but growing rapidly: nine of the 14 included studies were published since 2023, five are randomized trials, and coverage is strongest for cash transfers and floods. Intrahousehold and community-level effects, long-term resilience, and cost-effectiveness are priority questions for the next phase. Advancing the field will require harmonizing outcome measures, expanding sectoral coverage, standardizing costing approaches, and testing the integration of AA with social protection and other systems. Addressing these priorities will enable AA to scale across diverse hazards and contexts with greater impact.