Prior research has demonstrated that migration intentions are a moderate to strong predictor of individual‐level migration across a wide range of countries, but their value for predicting community‐level population change remains unclear. Analyses of census data 1972–2012 and a population survey of Icelandic adolescents in 1992 show that each percentage point difference in adolescent migration intentions is associated with 1.36 per cent change in the surveyed cohort and 1.25 per cent change in the total population over a 20‐year period. Roughly half of the predictive value of migration intentions can be attributed to remoteness and long‐term population change prior to the survey. On average, communities only experienced long‐term population decline when more than half the adolescent population had intended to leave, but lower levels of adolescent migration intentions are associated with changes in the age composition. These results strongly suggest that adolescent migration intentions signal future population development.