Background/objectives: Cognitive flexibility is the mental skill that allows a person to shift between different ideas or concepts and think about several concepts simultaneously. A commonly used tool to assess cognitive flexibility is the Cognitive Flexibility Scale (CFS). This study focused on translating and validating the CFS into Arabic, given the lack of existing Arabic tools for assessing cognitive flexibility. Methods: Conducted at King Saud University, Riyadh, between April and June 2024, the study employed random sampling and involved 529 participants, including 419 students and 110 patients. Results: The average participant age was 25.8 years, with females making up 56.9% of the sample. Participants completed the Arabic CFS, along with the Emotion Regulation Questionnaire (ERQ) and the Perceived Stress Scale (PSS), at two time points 3–6 weeks apart. Reliability was evaluated through internal consistency (Cronbach’s alpha = 0.8) and test–retest reliability (intraclass correlation coefficient = 0.82). Item analysis indicated that removing any single item did not significantly impact overall reliability, and inter-item correlations were strongest between items 4 and 6 (0.55) and items 6 and 7 (0.51). Validity was assessed through face, content, and construct validity, with factor analysis revealing a dominant single component accounting for 34.4% of the variance, confirming the scale’s unidimensionality. Content validity indices for all items exceeded 0.9 in terms of relevance, importance, simplicity, and clarity. The Arabic CFS demonstrated good construct validity, showing significant correlations with the ERQ’s reappraisal and suppression dimensions and the PSS. Conclusion: In conclusion, the Arabic version of the CFS is a valid and reliable tool for assessing cognitive flexibility in Arabic-speaking populations. This tool will be valuable in both clinical and research settings within Saudi Arabia, offering a robust instrument for evaluating cognitive flexibility.