Personality has a long history in psychology. It is one of the only streams of research that truly spans the breadth of the field, having arguably made important contributions in every major area of psychological study. However, the predictive utility of personality is generally regarded as disappointing, limiting the value of the practical application of personality research. One area in which this issue is particularly pertinent is personnel selection, where it has been suggested by some scholars that traditional personality measures be abandoned altogether. Although several attempts have been made to resolve the problem of personality and prediction through improved measurement, thus far these attempts have offered only limited gains. This thesis introduces a novel solution to this problem, central to which is an acknowledgement of the dynamic nature of personality, something extant approaches to measurement typically fail to account for. To this end, a novel construct termed âadaptive personality regulationâ is proposed. This is defined as, âan individual difference that reflects the extent to which people are able to successfully regulate their expression of personality in order to maximise goal attainment in their current situationâ. A theoretical framework that integrates adaptive personality regulation within the extant literature is described and criteria for determining proof of concept are presented. Study 1 sought to establish whether an investigation into adaptive personality regulation within a performance context was justified. In support of this, data from two independent samples of working adults revealed that employees in a wide variety of job roles perceive variation in personality expression to be necessary for them to perform well at work. Study 2 utilised a novel research paradigm to explicitly investigate the proposed construct of adaptive personality regulation for the first time. Results supported proof of concept with respect to a number of key criteria. Not only was there evidence that adaptive personality regulation exists as an individual difference and appears to operate as hypothesised, but also this construct was observed to account for significant amount of incremental variance in performance outcomes over and above personality traits (12%), cognitive ability (11%), and motivation (10%). Study 3 served to replicate and extend the findings of Study 2 with a new sample. Results revealed comparable effect sizes to those reported in the previous study, lending weight to the generalisabiltiy of results. In addition, the relationship between this construct and other theoretically similar variables not previously examined was considered. Not only was adaptive personality regulation found to be independent from these constructs, but it was also observed to account for significant incremental variance in performance outcomes over and above both self-control (19%) and adaptive performance (13%). The thesis concludes by considering the overall contribution made by this research. Limitations are noted and recommendations for future investigations into adaptive personality regulation are outlined.