AbstractRecent studies have shown that worry and related negative metacognitions are characteristic in generalized anxiety and paranoia respectively. However, most of these studies did not take into account common co-occurrence of anxiety and paranoia, and longitudinal modelling of the role of worry and metacognitions on the development of anxiety and paranoia is rare. The current study aimed at examining the bidirectional longitudinal relationship between anxiety and paranoia, as well as the importance of worry and metacognitions in the development of these symptoms. Our validated sample consisted of 2291 participants recruited from universities, among whom 1746 participants (76.21%) completed online questionnaires at baseline and at one year, reporting levels of anxiety, paranoia, worry, and negative metacognitions. Structural equation modeling analyses, followed by path comparisons, revealed that anxiety and paranoia mutually reinforced each other over time. Negative metacognitions, rather than worry itself, were contributive to the development of both symptoms over time. Negative metacognitions showed bi-directional relationships with anxiety over the time period assessed and showed uni-directional relationships with paranoia. Clinical implications of our findings are discussed.