This study aimed to comparatively assess cervical sagittal alignment, progression of ossification of the posterior longitudinal ligament (OPLL), and health-related quality of life (HRQOL) outcomes between patients who underwent cervical laminoplasty (CL) and those who underwent cervical laminectomy with fusion (LF) for cervical OPLL at more than three levels. We retrospectively evaluated consecutive 91 patients with cervical OPLL undergoing CL (n = 49) or LF (n = 42) who were followed up for at least 24 months (mean 38.6 months). We analyzed radiological measurements (C2-7 sagittal vertical axis [C2-7 SVA], C0-2 angle, C2-7 lordotic angle, T1 slope, and range of motion [ROM]), OPLL thickness, and clinical outcomes (visual analog scale [VAS], neck disability index [NDI], Short Form-36, and Japanese Orthopaedic Association [JOA] scores). Compared with preoperative levels, postoperative C2-7 SVA increased significantly increased in the LF (15.05 mm) and CL (7.86 mm) groups (P = 0.0021). Loss of cervical lordosis and ROM was significantly larger in the cervical LF group (P = 0.0296, P = 0.0004). Improvements in HRQOL, JOA recovery ratio, and VAS were similar between both groups, while NDI improved more significantly in the CL group (P = 0.0425). The postoperative neck VAS correlated positively with the change (Δ) of C2-7 SVA (P = 0.0174) and negatively with the change (Δ) of C2-7 lordotic angle (P = 0.0354). Progression of OPLL thickness in the LF (0.31 ± 0.37 mm) was significantly smaller than in the CL group (1.09 ± 0.64 mm) (P < 0.0001). CL was superior to LF in preserving cervical ROM, preoperative cervical lordosis, and minimizing neck disability. The stabilization obtained by adding instrumented fusion could suppress the progression of OPLL thickness.