Previous studies have shown that institutional trust is associated with people’s support for some environmental policies (e.g., support for higher taxation) but not others (e.g., support for subsidies and bans). Such findings seem to contradict the notion that institutional trust helps to resolve social dilemmas and thus facilitates collective action on environmental problems. In the current study, we use the conceptual framework of the attitudinal theory of the Campbell paradigm to understand the lack of institutional trust as a behavioral cost of policy support which counterweights people’s motivation to support a policy. Using a dataset from the Environmental module of a recent ISSP survey conducted in 28 countries, we corroborated the theoretical prediction, namely the expected positive effect of institutional trust on support for both pro- and anti-environmental policies. We also corroborated, albeit with some qualifications, that the choice of environmental policy depends on perceived behavioral costs exemplified, in our study, by institutional trust. The Campbell paradigm provides a useful analytical framework for understanding the role of trust in environmental policy support. It also helps us to understand previous inconsistent findings regarding the effect of trust on environmental policy support.