Cost-effective conservation strategies are needed because resources for nature conservation are often limited. When areas of high biodiversity value rest on private land, voluntary participation of landowners to conservation should be sought. Voluntary programs are still rarely implemented and evaluated in their effectiveness in achieving conservation targets. From 2000 onwards, a conservation program was conducted to preserve raptor nests from forest clear-cutting in private lands of North Karelia (Finland). Landowners were proposed to voluntarily set aside a forest buffer around nests of Accipiter gentilis, Buteo buteo and Pernis apivorus on their land. Participation was based on self-motivation, with no incentive involved. Participation to the program was extremely high (97% of 327 approached landowners during 2002–2006 joined). This positive attitude reduced nest losses as a result of forestry from 54% in the 1990s (n = 327 known nests) to only 2% since the start of the program (n = 519 nests). The voluntary action proved effective as a before-after-control-impact analysis showed that low-buffered nests (which had clear-cutting within 100 m; n = 48) had similar occupancy as high-buffered nests (no clear-cutting within 100 m; n = 144). Occupancy, however, decreased with shorter distance to the clear-cut within the 100 m radius, and thus as wide a buffer as possible is recommended to retain occupancy of a nest site. We conclude that voluntary-based approaches can be useful for cost-effective conservation and they should be considered more often in conservation practice.