Introduction: Decreased motivational tendency to seek out, engage in, and enjoy investing in complex cognitive processes in a sustained manner (need for cognition; NFC) may be a predictor and consequence of heightened anxiety and depression symptoms (ADS).However, the majority of investigations on this topic have been cross-sectional, which hinders causal inferences. Methods: The current study thus determined the within-person relations between NFC and ADS by using random intercept cross-lagged panel model (RI-CLPM) and bivariate dual latent change score (BLCS) approaches to separate between-and within-person effects. RI-CLPM and BLCS also present with advantages of adjusting for regression to the mean, baseline scores, autoregressive and lagged effects, and minimizing measurement error. Community-dwelling adults (n = 6750) completed the Mental Health Inventory-5 and trait-level NFC scales approximately every one year across 10 years. Results: RI-CLPM showed that within persons, lower level of NFC predicted higher future level of ADS, and vice versa (d = -0.852 to -0.498). Likewise, BLCS demonstrated that within persons, smaller change in NFC forecasted larger subsequent increase in ADS, and conversely (d = -0.631 to -0.519). Findings remained after adjusting for socio-demographic covariates. Conclusion: Consistent with theories, findings suggested that the within-person level-to-future level and change-to-future change relations among NFC and ADS were bi-directional and negative, with moderate-to-large effect sizes. Targeting NFC may treat or prevent the emergence of depression and anxiety disorders. Such efforts may include augmenting or personalizing evidence-based cognitive behavioral therapeutic strategies for individuals with or at-risk for heightened ADS.