Stimuli conditioned with a substance can generate drug-approach behaviors due to their acquired motivational properties. According to implicit theories of addiction, these stimuli can decrease cognitive control automatically. The present study (n = 49) examined whether reward-associated stimuli can interfere with cognitive processes in the absence of knowledge about stimulus--outcome contingencies. Conditioned stimuli (CS) were paired with high-reward (HR) or low-reward (LR) probabilities of monetary reward using a Pavlovian learning task. Participants were categorized as Aware or Unaware of contingencies using a Bayesian analysis. CS were then used as task-irrelevant distractors in modified flanker and N-back tasks. Results show HR CS can generate increased interference in the flanker task for participants Unaware of contingencies, contributing further evidence for the existence of implicit Pavlovian conditioning. For the N-back task, working memory performance was affected by HR CS, albeit only for Aware participants. These results suggest that CS can interfere implicitly with cognitive processes in a similar way to drug-related stimuli. Such an effect could occur in a stimulus-driven fashion, devoid of top-down goal-directedness. These findings have implications for the conceptualization and study of implicit processes in addiction and highlights the necessity to reconsider the measurement of such phenomena.