Return migration is key to community recovery from many disasters. Japanese governments have conducted radiation decontamination efforts in the Exclusion Zone designated after the 2011 Fukushima nuclear disaster in order to encourage this outcome. Little is known, however, about the factors that influence post-disaster migrants to return, and, if people are relatively unresponsive to decontamination, then the costs of promoting recovery may exceed the benefits. We exploit a unique survey of Fukushima evacuees to determine the factors that influence their decision to return after a disaster. Location-specific capital characteristics, such as housing tenure and the extent of property damage, are estimated to be strong factors. The radiation dose rate of the home location is found to be a statistically significant factor for intent to return, but its effect is small. We also found that households with various other characteristics were noncommittal about the return option and likely to defer their decisions, which implies that "return" and "not-return" are asymmetric. Our simulation analysis found that the number of returnees encouraged by this decontamination was 14,367, less than 10% of the total evacuees, while the decontamination cost per returnee was 3.0 million USD. This result implies that the government could have improved the well-being of evacuees at a lower cost by policies other than decontamination.