Ten years ago, Madagascar’s government committed to drastically scale up the nation’s protected-area coverage from ~3% to 10% of its area. We ask how successful this PA expansion is likely to be in terms of reducing deforestation (and, thereby, increasing the conservation of biodiversity). We statistically evaluate the impact of the prior generations of Malagasy PAs and use those results to anticipate the conservation impacts of Madagascar’s newest PAs. We find that deforestation was reduced by the prior PAs, although by less than suggested in simpler comparisons that lack explicit controls for land characteristics. Further, impacts are higher where deforestation pressure is higher, which often is closer to roads and cities (and which also may imply higher costs). We find Madagascar’s newest PAs are sited where, if managed correctly, they can achieve impacts at least as high as prior conservation.