Objectives <p>Trait mindfulness—one’s disposition toward non-judgmental awareness of present-moment experience—has been associated with various affective and cognitive outcomes. One proposed mechanism is that this kind of mindfulness attenuates the tendency to become attached to some experiences and avoid others. In line with this, a previous study reported that trait mindfulness reduced the development of affective preferences for letter strings that, unbeknownst to participants (<i>n</i> = 18), followed a specific grammatical structure. If robust, this finding would confirm that trait mindfulness reduces implicit affective biases. In this pre-registered study, we aimed to replicate this main finding with a much larger sample size (<i>n</i> = 127) and also explored whether prior meditation experience influenced implicit preference formation.</p> Method <p>Trait mindfulness was measured in 127 participants using the Five Facet Mindfulness Questionnaire. Over five days, participants were exposed to strings of apparently random letters, some of which conformed to an artificial grammar. They reproduced these strings in a working memory task and later rated whether they liked them, providing an index of implicit preference.</p> Results <p>We replicated basic artificial grammar learning effects but found no association between trait mindfulness and implicit preference development. Meditation experience similarly showed no effect on preference formation.</p> Conclusion <p>We did not replicate the previously reported effect of trait mindfulness on implicit preferences with our larger sample and improved design. Preference development may be too automatic to be modulated by mindfulness. Alternative explanations are also discussed.</p> Preregistration <p>This study was preregistered on the OSF (<a href="https://osf.io/tsnfp">https://osf.io/tsnfp</a>).</p>