This study will investigate if nivolumab will improve recurrence-free survival (RFS) compared to placebo in participants with HCC who have undergone complete resection or have achieved a complete response after local ablation, and who are at high risk of recurrence

Inclusion Criteria:

• Participants with a first diagnosis of HCC who have undergone a curative resection or ablation
• Participants are eligible to enroll if they have non-viral related-HCC, or if they have HBV-HCC, or HCV-HCC
• Child-Pugh Score 5 or 6
• Eastern Cooperative Oncology Group (ECOG) performance status (PS) 0 or 1

Exclusion Criteria:

• Known fibrolamellar HCC, sarcomatoid HCC, or mixed cholangiocarcinoma and HCC
• Any evidence of tumor metastasis or co-existing malignant disease
• Participants previously receiving any prior therapy for HCC, including loco-regional therapies
• Participants who have undergone a liver transplant or those who are in the waiting list for liver transplantation
• Participants who have received a live/attenuated vaccine within 30 days of randomization (eg, varicella, zoster, yellow fever, rotavirus, oral polio and measles, mumps, rubella [MMR]).

Other protocol defined inclusion/exclusion criteria apply