Conflicts of interest, situations where personal or organizational considerations have compromised or biased professional judgment and objectivity, can weaken scientific credibility, pose threats to biodiversity and ecosystem services, and are often precursors to corruption. Here, we review historical and international examples of conflicts of interest and their impacts on global biodiversity. We present a contemporary example of a conflict of interest that might have implications for the U.S. Environmental Protection Agency's re-evaluation of the safety of the herbicide atrazine. To help scientists, natural resource managers, policy makers, and judicial officials identify and thwart conflicts of interest, we review strategies used by individuals and organizations with conflicts of interest to evade environmental and public health decisions, discuss the role of the scientific and governmental review processes in maintaining scientific integrity, and offer recommendations to reduce bias and facilitate sound and swift decision making for enhanced environmental health.