The relationship between agricultural support policies (adapted from the OECD Producer Support Estimate (PSE) classification) and a selection of environmental impacts are analysed in a range of country settings, using a farm-level and a market-level model. Based on the methods and environmental indicators used, market price support and payments based on unconstrained variable input use were the most environmentally harmful among the various PSE measures. Decoupled support payments based on non-current crop area were the least harmful, even when considering their impacts on the behaviour of risk averse farmers. The impacts of support policies that clearly change the competitiveness of one production activity in relation to another, such as payments based on current crop area or on animal numbers, were more equivocal. Support payments subject to environmental constraints can improve environmental outcomes compared to coupled support without restrictions, however, they can also have unintended environmental impacts.