AbstractPopulist radical right parties are on the rise all over Europe. Recent literature investigates their effects on environmental policy, however, often applying an overly broad perspective on the policy area and neglecting causal mechanisms. This article addresses both gaps in an in‐depth case study of partisan effects on Swedish environmental policy in the wake of increasing populist radical right influence. A novel data approach deriving party positions and policy output from the hard figures of budget proposals between 2001 and 2023, allows a nuanced analysis of environmental policy and its subsectors (e.g., nature conservation and climate mitigation). In summary, a traditional partisan effect is confirmed as a major explaining factor for environmental policy change, while the effect unfolds through altered coalition formation strategies leading to the exclusion of “green voices.” This brings to the fore interactive environmental policy effects of the populist radical right and center‐right parties in the context of changing party competition constellations more generally.