Recovery is a diffuse concept that is poorly and inconsistently defined in the gambling literature. There are no established operational criteria for recovery from gambling disorder, thus making it difficult to make cross-study comparisons and determine treatment efficacy. This thesis aimed to increase understanding of recovery in gambling disorder by developing and validating a self-report instrument for the measurement of gambling recovery. Chapters 1 and 2 contain a review of the literature on theoretical models relevant to recovery, and measurement of treatment outcomes in gambling disorder. Findings were used to specify the conceptual boundaries of gambling recovery based on researchers’ previous attempts to define and measure this construct. In Chapter 3, a series of qualitative interviews were conducted with gamblers accessing formal help services to better understand their conceptualisations of recovery. In Chapter 4, an integrated construct definition and an initial pool of questionnaire items were developed. In Chapter 5, draft items were subjected to review and refinement via expert feedback and cognitive pretesting. Psychometric evaluation of the recovery instrument in a larger sample of gambling treatment service users is detailed in Chapter 6. This analysis resulted in a 32-item solution across six recovery dimensions: gambling reduction, urge coping, recovery wisdom, life functioning, interpersonal relationships, and mental health. The recovery index for gambling disorder (RIGD) demonstrated good construct validity and test-retest reliability. The RIGD is the first instrument specifically designed to measure recovery in the gambling literature. Valid measurement of recovery is particularly important given the central role of this construct in shaping mental health service policy internationally.