The current thesis set out to develop an implicit relational assessment procedure as a measure of self-forgiveness across five studies. The first study targeted the development of a measure of implicit forgiveness of self related to “minor” transgressions (mistakes, flaws, shortcomings) versus the forgiveness of others. The results indicated that the measure of implicit forgiveness diverged from an explicit measure designed to measure the same construct. Moreover, implicitly, participants tended to be more forgiving towards themselves than towards others, whereas at the explicit level participants tended to forgive others. The second study aimed to develop the Implicit Relational Assessment Procedure (IRAP) as a measure of response biases related to emotional reactions and expected outcomes in the context of minor failings and successes in everyday life. However, in contrast to the previous study, the IRAPs were modified to investigate forgiveness of the self rather than others. Additionally, the research explored the extent to which such implicit reactions were related to standardized measures of psychopathology, including a measure Depression, Anxiety and Stress (DASS), measures of self-compassion (Self-Compassion Scale, SCS) and a scale that was based directly on the IRAP. Once again, the results showed that there was no convergence between explicit and implicit measures. The third study was similar to the second one, except that instead of using nomographic stimuli, ideographic stimuli were used with the IRAPs that reflected problem behaviours and the feelings (and anticipated outcomes) that they evoked in each one of the participants. Although specific response biases on the IRAP correlated with psychological suffering, particularly depression and stress, the results of the second and the third study were very similar in that only a few correlations were found between the explicit and implicit measures. Due to disclosure issues, the nomographic IRAPs developed in the second study were used in the next study. The fourth study investigated the impact of two priming procedures on implicit self-forgiveness. Specifically, participants had to write down 3 examples of failures or successes depending on priming condition (negative or positive priming); the researcher did not have access to what was written. Results indicated differences in the way in which the two types of priming impacted upon the IRAP effects, and how those effects correlated with measures of self-compassion and psychopathology. Finally, the final study aimed to investigate the impact of a history of training in behaviour therapy using the self-forgiveness IRAPs. Overall, only one of the two IRAPs, the one that targeted feelings rather than outcomes, produced clear and significant differences between the group with a history of therapy training versus a control group with no such training. The thesis concludes with a summary and a detailed discussion of the findings reported in each of the chapters. Overall, the research presented in the current thesis constitutes a first step in developing measures of the verbal behaviours involved in the psychological domain of self-forgiveness.