Recent empirical evidence suggested that low adherence to Recommended Health Behaviors (RHB) and the use of pseudo-scientific practices (PSP) during the COVID-19 pandemic is predicted by psychological predispositions that refer to various types of irrational thinking and beliefs. These are conspiratorial beliefs, cognitive intuition, and cognitive biases (Teovanović et al., 2020), experiential thinking style, and disintegration personality trait (proneness to psychotic-like experiences/behaviors) (Lazarević et al., 2021). Here, we focus on two constructs tightly related to irrational thinking, that are so far underexplored in relation to COVID-19 health behaviors. First is a specific set of irrational beliefs described by rational emotive behavior therapy (REBT) and second is adult attachment. This study aims to investigate REBT irrational beliefs and attachment dimensions as mediators of the relationship between personality traits and COVID-19 health behaviors. We also included a third mediator - conspiracy mentality, as an already established predictor of both nonadherence to RHB and PSP.