There is little systematic knowledge about the magnitude and allocation of international funding flows to support biodiversity conservation in the developing world. Using the newly released AidData compilation, we present a comprehensive assessment of official donor assistance for biodiversity during 1980–2008. We find that biodiversity aid increased markedly in the early 1990s, but that estimates of current aid are likely overstated and donor commitments at the 1992 Rio Earth Summit have not been met. Aid has been well targeted, however, in that the allocation of biodiversity aid is positively associated with the number of threatened species in recipient countries after controlling for country size, national population, and wealth. Biodiversity aid is also positively associated with indicators of good governance. Our results provide an empirical measure of progress toward international conservation funding targets, a baseline against which future flows can be compared, and information necessary to assess the effectiveness of biodiversity aid.