Background. The Functional Rating Index (FRI) is a self-report scale widely used to determine the level of disability in low back pain (LBP) populations. Objectives. This study was aimed at conducting the cross-cultural adaptation of the FRI-Arabic version (FRI-Ar) and testing the clinometric properties of FRI-Ar. Methods. The cross-cultural adaptation process was used to develop the FRI-Ar. This study included acute and subacute LBP patients. Each patient was asked to complete the questionnaires at three time points: baseline, 24-hour follow-up, and two-week follow-up. The questionnaires used were FRI-Ar, Roland-Morris Disability Questionnaire (RMDQ), Oswestry Disability Index (ODI), Numerical Pain Rating Scale (NPRS), Global Perceived Effect Scale (GPE), and Patient-Specific Functional Scale (PSFS). Statistical analysis was carried out to measure the instrument’s reliability, validity, and responsiveness. Results. The FRI was cross-culturally adapted to the Arabic language, and the adapted version was validated. Two hundred patients completed the questionnaires at the baseline; however, 120 patients completed the questionnaires at 24-hour and two-week follow-up. Cronbach’s alpha, interclass correlation coefficient (ICC2,1), standard error of measurement (SEM), and minimal detectable change (MDC95%) for the FRI-Ar were observed as 0.85, 0.85, 1.17 (2.9%), and 3.24, respectively. The FRI-Ar showed a moderate positive correlation only with the RMDQ, ODI, and NPRS ( p < 0.05 ). Also, it showed the responsiveness with a small effect size ( ES = 0.29 ) and standardized response mean ( SRM = 0.44 ). Conclusion. The FRI-Ar was developed, and it showed good reliability and validity. However, it revealed the responsiveness with the small change. It can evaluate both pain and functional limitations in acute and subacute LBP patients. Before using it in the Arabic population with acute and subacute LBP, it is recommended to conduct further research to test internal and external responsiveness using an external criterion with a more extended follow-up period and suitable interventions.