Inclusion Criteria:

          -  Unresectable or metastatic soft tissue sarcoma

          -  ≥ 1 prior systemic therapy for sarcoma, including adjuvant systemic therapy

          -  Age ≥ 18 years

          -  4 Life expectancy > 3 months

          -  Eastern Cooperative Oncology Group (ECOG) performance status 0 or 1

          -  Lab values as below:

        Absolute neutrophil count (ANC) ≥ 1,000/mm^3 Platelet count ≥ 75,000/mm^3; Creatinine ≤ 1.5
        x upper limit of normal (ULN) OR calculated (calc.); creatinine clearance > 45 mL/min using
        the lean body mass formula only; Total bilirubin ≤ 1.5 x ULN in absence of Gilbert disease
        (total bilirubin ≤ 3 x ULN with Gilbert); also, if hyperbilirubinemia is clearly attributed
        to liver metastases total bilirubin ≤ 3 x ULN is permitted AST/ALT ≤ 3 x ULN;Thyroid
        stimulating hormone (TSH) within normal limits (WNL);supplementation is acceptable to
        achieve a TSH WNL; in subjects with abnormal TSH if free T4 is normal and subject is
        clinically euthyroid, subject is eligible

          -  Any toxic effects of prior therapy (except alopecia) must be resolved to NCI CTCAE,
             version 5.0, Grade 1 or less

          -  Ability to understand and the willingness to sign a written informed consent

          -  Women of childbearing potential (WOCBP) receiving nivolumab must be willing to adhere
             to contraception for a period of 5 months after the last dose of nivolumab. Men
             receiving nivolumab and who are sexually active with WOCBP will be instructed and must
             be willing to adhere to contraception for a period of 7 months after the last dose of
             nivolumab.

        Exclusion Criteria:

          -  Prior therapy with ipilimumab or nivolumab, or any agent targeting programmed cell
             death 1 (PD-1), PD-L1 or cytotoxic T-lymphocyte-associated protein 4 (CTLA-4)

        History of the following:

          -  Active known or suspected autoimmune disease

          -  Known human immunodeficiency virus (HIV) (Subjects with lymphocytes > 350 cluster of
             differentiation (CD)4+ cells and no detectable viral load are eligible)

          -  Hepatitis B

        Hepatitis B can be defined as:

        Hepatitis B surface antigen (HBsAg) > 6 months Serum hepatitis B virus (HBV)
        deoxyribonucleic acid (DNA) 20,000 IU/mL (105 copies/mL), lower values 2,000 to 20,000
        IU/mL (104 to 105 copies/mL) are often seen in hepatitis B-e antigen (HbeAg)-negative
        chronic hepatitis B Persistent or intermittent elevation in alanine aminotransferase
        (ALT)/alanine aminotransferase (AST) levels. Liver biopsy showing chronic hepatitis with
        moderate or severe necroinflammation

          -  Hepatitis C Hepatitis C antibody (Ab) positive Presence of hepatitis C virus (HCV)
             ribonucleic acid (RNA) 3.2.2.5 Known active pulmonary disease with hypoxia defined as:
             Oxygen saturation < 85% on room air or Oxygen saturation < 88% despite supplemental
             oxygen

          -  Systemic treatment with either corticosteroids (> 10 mg daily prednisone equivalents)
             or other immunosuppressive medications within 7 days of registration

          -  Received any live/attenuated vaccine (eg, varicella, zoster, yellow fever, rotavirus,
             oral polio and measles, mumps, rubella (MMRI) within 30 days before initiation of
             treatment on this protocol.

          -  If female, pregnant or lactating. (Women of childbearing potential are required to
             have a negative pregnancy test within 24 hours prior to the initial administration of
             study drug)