Training interventions have been proposed as a countermeasure against greenwashing. However, there is no clear consensus on their effectiveness. In an effort to contribute to a better understanding, we examined the impact of greenwashing training on consumers’ ability to discern greenwashing using an online survey experiment designed to resolve ecological and internal validity issues of past work (N = 518). Additionally, we extended the scope by exploring whether greenwashing training also affects healthwashing detection. Our study revealed that greenwashing training can make consumers more likely to perceive advertisements featuring deceptive environmental claims correctly as greenwashing but can also make them more likely to misperceive advertisements without such claims as greenwashing. Furthermore, it showed that although healthwashing is not the subject of greenwashing training, the triggered skepticism can transfer to healthwashing perceptions, too. Overall, these findings suggest that greenwashing training does not enhance greenwashing detection proficiency but rather promotes excessive suspicion.