Individuals with disabilities who engage in regular physical activity reduce their risk of diseases such as obesity and heart disease, as well as other risk factors; relieve tense emotions, and improve their quality of life via interaction with others. Despite these advantages, only one out of every four Koreans with a disability engages in physical activity. Grit is the ability to maintain interest and effort towards a goal in the face of adversity and failure. Grit can act as an important factor in increasing the psychological level of individuals with disabilities. We investigated the relationship between basic psychological needs, grit, and the quality of life of disabled individuals to determine if physical activities can improve their quality of life. Our dataset included 296 disabled individuals registered with the Korean Ministry of Health and Welfare. Using structural equation modelling, the direct and indirect effects of grit, quality of life, and psychological needs satisfaction such as competence, relatedness, and autonomy were examined. We found that competence positively affects consistency of interests (β = 0.150, t = 1.854), relatedness positively affects consistency of interests (β = 0.354, t = 4.409), and autonomy has no statistically significant effects (β = 0.101, t = 1.086). Second, competence positively affects perseverance of effort (β = 0.249, t = 3.206), autonomy negatively affects perseverance of effort (β = −0.269, t = −2.880), and relatedness has no statistically significant effects (β = −0.017, t = −0.249). Third, autonomy positively affects quality of life (β = 0.214, t = 2.349) while competence and relatedness had no statistically significant effects (β = −0.018, t = −0.208; β = 0.096, t = 1.288). Fourth, consistency of interests positively affects quality of life (β = 0.312, t = 4.191) while perseverance of effort had no statistically significant effects (β = −0.094, t = −1.480). Fifth, competence was found to have positive indirect effects on quality of life through grit. This study underscores the importance of addressing these three basic psychological needs and elements of grit when designing future quality of life interventions for disabled individuals.