► we analyzed how dynamics and uncertainty in species distributions may affect conservation planning decisions. ► A new version of the Marxan software was developed to deal with uncertainty in species distributions. ► A set of sites in the Iberian Peninsula were identified, where conservation investment is robust to uncertainty. Climate warming challenges our approach to building systems of protected areas because it is likely to drive accelerating shifts in species distributions, and the projections of those future species distributions are uncertain. There are several important sources of uncertainty intrinsic to using species occurrence projections for reserve system design including uncertainty in the number of occurrences captured by any reserve selection solution, and uncertainty arising from the different approaches used to fit predictive models. Here we used the present and future predicted distributions of Iberian herptiles to analyze how dynamics and uncertainty in species distributions may affect decisions about resource allocation for conservation in space and time. We identified priority areas maximizing coverage of current and future (2020 and 2080) predicted distributions of 65 species, under “Mild” and “Severe” uncertainty. Next, we applied a return-on-investment analysis to quantify and make explicit trade-offs between investing in areas selected when optimizing for different times and with different uncertainty levels. Areas identified as important for conservation in every time frame and uncertainty level were the ones considered to be robust climate adaptation investments, and included chiefly already protected areas. Areas identified only under “Mild” uncertainty were considered good candidates for investment if extra resources are available and were mainly located in northern Iberia. However, areas selected only in the “Severe” uncertainty case should not be completely disregarded as they may become climatic refugia for some species. Our study provides an objective methodology to deliver “no regrets” conservation investments.