Background and Aims Limited evidence exist regarding the association between ongericimab, a novel recombinant humanized anti-PCSK9 monoclonal antibody, and primary hypercholesterolemia and mixed dyslipidemia. This study aimed to evaluate the efficacy and safety of ongericimab administered by prefilled syringe (PFS) or autoinjector (AI) in Chinese patients with primary hypercholesterolemia and mixed dyslipidemia on stable optimized lipid-lowering therapy. Methods and Results A total of 255 patients on stable optimized lipid-lowering therapy were randomized in a 2:1:2:1 ratio to receive PFS for the subcutaneous injection of ongericimab 150 mg every 2 weeks (Q2W) or a matching placebo, or AI for the subcutaneous injection of ongericimab 150 mg Q2W or a matching placebo. The primary efficacy endpoint was the percent change in low-density lipoprotein cholesterol (LDL-C) levels from baseline to week 12. Safety was also evaluated. At week 12, the least squares mean percent changes were -72.7% (3.9%) for PFS and -71.1% (3.8%) for AI (all P<0.001) compared to respective matching placebo groups. Beneficial effects were also seen for all secondary lipid parameters, notably with robust reduction in Lp (a). Treatment-emergent adverse events (TEAEs) and serious AEs with ongericimab were reported in 46.2% and 2.4% of patients, compared to 44.2% and 3.5% with placebo. Conclusion In Chinese patients with primary hypercholesterolemia and mixed dyslipidemia, a 12-week treatment regimen with ongericimab administered by PFS or AI significantly reduced LDL-C and other lipid parameters, proving to be safe and well tolerated. Patients experienced consistent effects from PFS or AI devices. Clinical trial registration CTR20220027; January 11, 2022; http://www.chinadrugtrials.org.cn/index.html.