A novel reflective writing exercise based on self-determination theory was created, applied, and assessed within the current study. The study aimed to examine the potential for this exercise to increase participants self-determination and perceived self-competence in relation to their long-term goal. 155 participants took part in the study, with 84 participants receiving the self-determination theory based reflective writing exercise, while the control condition (n = 71) received a control intervention. Total self-determination score and perceived self-competence were assessed at baseline, and again following the intervention. A mixed two way ANOVA revealed a significant increase in the intervention conditions total self-determination, while the control condition showed no significant change. A Mann Whitney U test and a Wilcoxon signed rank test revealed that both the experiment and control condition showed significant increases in perceived self-competence following the intervention. No gender or age differences were evident in relation to the effectiveness of the intervention for the experiment condition. Limitations and recommendations for future research are discussed.