Decision transparency is often proposed as a way to maintain or even increase citizen trust, yet this assumption is still untested in the context of regulatory agencies. We test the effect of transparency of a typical decision tradeoff in regulatory enforcement: granting forbearance or imposing a sanction. We employed a representative survey experiment (n = 1,546) in which we test the effect of transparency in general (providing information about a decision or not) and the effect of specific types of transparency (process or rationale transparency). We do this for agencies supervising financial markets, education, and health care. We find that overall decision transparency significantly increases citizen trust in only two of the three agencies. Rationale transparency has a more pronounced positive effect only for the Education Inspectorate. We conclude that the overall effect of decision transparency is positive but that the nature of the regulatory domain may weaken or strengthen this effect.