Background The cross‐lagged panel (regression) model ( CLPM ) is the usual framework of choice to test the longitudinal reciprocal effects between self‐concept and achievement. Criticisms of the CLPM are that causal paths are over‐estimated as they fail to discriminate between‐ and within‐person variation. The random‐intercept cross‐lagged panel model ( RI ‐ CLPM ) is one alternative that extends the CLPM by partialling out between‐person variance. Aims We compare analyses from a CLPM and a RI ‐ CLPM which examine the reciprocal relationships between self‐concept, self‐efficacy, and achievement and determine the extent CLPM estimates are inflated by between‐person variance. Sample(s) Participants ( n = 314) were first‐year undergraduate psychology students recruited as part of the ST udent Engagement with Education and Learning ( STEEL ) project. Methods Participants completed measures of self‐efficacy and self‐concept prior to completing fortnightly quiz assessments. Results Cross‐Lagged Panel (regression) Model estimates are likely over‐estimated in comparison with RI ‐ CLPM estimates. Cross‐Lagged Panel (regression) Model analyses identified a reciprocal effects relationship between self‐concept and achievement, confirming established literature. In RI ‐ CLPM analyses, these effects were attenuated and a skill development association between achievement and self‐concept was supported. A reciprocal relationship between self‐efficacy and achievement was supported. Better model fit was reported for the RI ‐ CLPM analyses. Conclusions Prior findings relating to the reciprocal effects of self‐concept and achievement need to be reconsidered. Whilst such a relationship was supported in a CLPM analysis in this study, within an RI ‐ CLPM framework, only achievement predicted self‐concept. However, in both CLPM and RI‐CLPM models a reciprocal effects model of self‐efficacy and achievement was supported.