When annual migration data lack reliability, scholars apply alternative methods for estimating international migration. Yet, researchers note that alternative approaches have primarily been tested on developed countries, rather than developing countries that usually have dramatic migration shifts. I close this research gap. I use the example of 15 former Soviet republics to demonstrate several conclusions. First, I show that such alternative approaches as immigration‐by‐origin data of receiving countries do not result in reliable and valid estimates of post‐Soviet migration, given the large variation that exists in how former Soviet republics define “migrant”. Second, I demonstrate that population censuses, while a more superior alternative, fail to capture temporary migrants. In developing countries, the international emigration is mainly due to temporary (undocumented labour) migration. Third, I suggest that scholars and policy‐makers should apply household surveys as a possible alternative. However, while this method seems promising, given the limited use of household surveys in migration measurement in the post‐Soviet republics, future research by both scholars and applied researchers should explore the advantages and limitations of household surveys as an alternative source for estimation of migration. Finally, I outline methodological guidelines that researchers and scholars can advance on migration issues in the post‐Soviet region.