["Journal of Research on Adolescence, Volume 36, Issue 3, September 2026. ", "\nAbstract\nIrritability and executive function, which continue to develop from late childhood to early adolescence, predict important functional impairments. Although correlated, longitudinal research has often focused only on how executive function affects irritability, overlooking the reverse pathway. This study proposes that irritability may also contribute to later executive function difficulties and investigates their bidirectional associations across three components, including inhibitory control, working memory, and cognitive flexibility, as well as whether these associations vary by sex. Random‐intercept cross‐lagged panel models were applied to data drawn from four waves of a longitudinal study involving 491 participants (Mage = 9.84 years, SD = 0.71; 48.1% boys), collected in June 2021, December 2021, June 2022, and March 2023. Results showed that inhibitory control consistently predicted later irritability across waves, with a reciprocal effect emerging in early adolescence. For working memory, a bidirectional relationship appeared earlier, with irritability consistently predicting later working memory. For cognitive flexibility, only a unidirectional effect was found, where earlier cognitive flexibility predicted later irritability, with no reverse effect. Sex moderated only the effect of cognitive flexibility at T3 on irritability at T4. These within‐person findings regarding irritability–executive function dynamics suggest that improving inhibitory control and cognitive flexibility may reduce irritability, while lowering irritability could benefit working memory, with no need for sex‐differentiated approaches.\n"]