The purpose of the present study was to assess the associations between academic commitment theory (operationalised as meaningful commitment) (Human-Vogel & Rabe, 2015), and self-determination theoretical constructs (operationalised through need support, need satisfaction, autonomous self-regulation and perceived competence) (Deci & Ryan, 2000) in predicting the academic achievement levels of South African Gr 11 and 12 learners. Data was collected on two occasions; participants initially completed a survey and I then obtained their average academic marks. Participants reported average to higher levels of measured constructs and responses on all measurements displayed a normal distribution. I used path analysis to test two hypothesised and several additional models. The results indicated that neither autonomous self-regulation nor meaningful commitment directly predicted academic achievement but that both constructs indirectly predicted academic achievement through basic psychological need satisfaction and perceived competence. Meaningful commitment, furthermore, predicted twice as much variance in need satisfaction as autonomous self-regulation, and was a significant predictor of autonomous motivation. The findings of this study provide some insight into the role of meaning in self-determination theory, as well the organising role of meaningful commitment in self-regulating behavioural choices. These findings may also help educators and policy makers to create learning environments in which learners’ need for meaning and self-determination is supported, so that they can achieve academic success. Methodologically, the present study contributes to the validation of the meaningfulness subscale and the application of self-determination theory instruments in a South African context. / Thesis (PhD)--University of Pretoria, 2017. / Educational Psychology / PhD / Unrestricted