Diabetes mellitus (DM) was a well-known risk factor for poor results after cervical spine surgery. In diabetic patients, hemoglobin A1C (HbA1c), a proxy for long-term glycemic management, was a helpful evaluation tool. For a study, researchers sought to find the ideal HbA1c levels in patients undergoing elective cervical spine surgery so that one could 1) maximize 1-year postoperative patient-reported outcomes (PROs) and 2) predict the incidence of medical and surgical problems. In a single academic center, retrospective cohort research was conducted utilizing prospectively collected data. Diabetic individuals who had an anterior cervical fusion or a posterior cervical laminectomy and fusion (PCLF) between October 2010 and March 2021 were included in the research. Furthermore, 408 diabetic patients were among the 1,992 registry participants who underwent cervical surgery. Anterior: A total of 259 diabetes patients had an anterior cervical fusion, with 141 of them having an HbA1c level accessible during the study period. The average age was between 55.8 and 10.1, and the intermediate HbA1c level was between 7.2 and 1.4. HbA1c levels over 6.1 were linked with failure to meet the minimum clinically significant difference (MCID) for Neck Disability Index (NDI) (AUC=0.77, 95% CI 0.70–0.84, P<0.001), while HbA1c levels above 6.8 were linked with a higher risk of reoperation (AUC=0.61, 95% CI 0.52–0.69, p=0.078). Posterior: PCLF was performed on 149 diabetic patients, 65 of whom had an HbA1c level available within a year. The average age was between 63.6 and 9.2, and the intermediate HbA1c level was between 7.2 and 1.5. HbA1c levels above 6.8 might have been associated with failure to achieve MCID for NRS-Arm pain (AUC=0.61, 95% CI 0.49–0.73, P=0.094), and HbA1c levels above 7.6 might have been associated with higher readmission rate (AUC=0.63, 95% CI 0.50–0.75, p=0.185), despite a low AUC for NRS-Arm pain and readmission. HbA1c levels above 6.1 were linked to a lower chance of obtaining MCID NDI in anterior cervical fusion surgery in a group of diabetic individuals undergoing elective cervical spine surgery. Though the superior outcomes of reoperation, readmission, and MCID for NRS-Arm pain showed only moderate associations, preoperative optimization of HbA1c using the levels as benchmarks should have been considered to reduce the risk of complications and maximize PROs for patients undergoing elective cervical spine surgery.