The Atlantic coast of South America supports many Nearctic shorebirds during their non-breeding season where they use a network of stop-over and wintering sites. To quantify the importance of French Guiana among those sites, we surveyed and resighted banded birds in the Kourou River estuary during two periods: 1989–1997 and 2005–2008. Twenty species were recorded, among which 15 were observed every year, during migration and/or boreal wintering. The most abundant species was Semipalmated Sandpiper (Calidris pusilla), accounting for 57% of all observations. In most Nearctic shorebird species, we observed dramatic changes in numbers and phenology between both survey periods. In the 1990s, the Kourou River estuary was mainly a post-breeding stop-over site; in the common shorebird species the largest numbers were observed in September and October. In the 2000s, only few species still occurred in significant post-breeding numbers, and migration peaks occured later for some of them. Observations of 304 banded individuals of five shorebird species indicated that some staging birds stopped in southern Canada and over-wintered in Brazil or Argentina. Many of our resighted birds stopped over in Delaware Bay in spring. Our results indicate the importance of French Guiana as a fall stop-over for Nearctic shorebirds using Western Atlantic Flyway.