BACKGROUND It is generally understood that postoperative C5 palsy can occur with anterior or posterior decompression surgery, but functional measures of the palsy have not been well documented. This study aimed to investigate the incidence of C5 palsy in different surgical procedures, examine the correlations between muscle strength, upper extremity functional measures, and health-related quality of life, and to observe potential risk factors contributing to C5 palsy. METHODS Our investigation involved a retrospective study design. A total of 364 patients who underwent decompression surgery were indicated within the selected exclusion criteria. Additionally, 12 C5 palsy patients were recruited. The relationships between the manual muscle test (MMT), the action research arm test (ARAT), the Jebsen test of hand function (JTHF), and the European quality of life-5 dimensions (EQ-5D) were studied, and univariate analyses were performed to search possible risk factors and recovery investigation. RESULTS The data analyzed in the 12 cases and C5 palsy incidences (3.3%) were: 0.7% in anterior procedures (n = 2), 8.8% in posterior procedures (n = 6), and 36.4% in combined procedures (n = 4). Moderate-to-high correlations were observed between the ARAT, JTHF, EQ-5D visual analog scale scores, and MMT (r = 0.636-0.899). There were significant differences in patient age, etiology of cervical lesion, variable decompression procedures, and the number of decompression levels between the C5 palsy and non-C5 palsy groups. For female patients (p = 0.018) and number of decompression levels (p = 0.028), there were significant differences between the complete recovery and the incomplete recovery groups. CONCLUSION Patients undergoing combined anterior-posterior decompression surgery had the highest incidence of C5 palsy, and correlations between the ARAT, JTHF, EQ-5D visual analog scale clinical tools, and MMT scores supported these findings. Female status and lower decompression levels could also be predictive factors for complete recovery, although additional research is needed to substantiate these findings.