The purpose of this study is to determine the recommended phase 2 dose(s) (RP2D[s]) of JNJ-87562761 in Part 1 (dose escalation), and to determine the safety and tolerability at RP2D in Part 2 (dose expansion) in participants with multiple myeloma (MM) whose disease has come back after treatment (relapsed) or hasn't responded to treatment (refractory).

Inclusion Criteria:

• Relapsed, refractory multiple myeloma with measurable disease defined as: (a) Serum monoclonal paraprotein (M-protein) level greater than (>)0.5 grams per deciliter (g/dL); or (b) Urine M-protein level >200 milligrams per 24 hours (mg/24 hours); or (c) Light chain multiple myeloma: serum immunoglobulin free light chain (FLC) >10 milligrams per deciliter (mg/dL) and abnormal serum immunoglobulin kappa-lambda FLC ratio
• Must have had prior therapy including a proteasome inhibitor, immunomodulatory agent and anti-CD38 therapy
• Have an eastern cooperative oncology group (ECOG) performance status of 0 to 1
• Have an estimated glomerular filtration rate (eGFR), of > 30 millilitres (mL)/min/1.73 meter square (m^2) computed per 2021 chronic kidney disease epidemiology collaboration (CKD-EPI) creatinine equation
• While on study treatment and for 6 months after the last dose of study treatment, a participant must: (a) Not breastfeed or be pregnant; (b) Not donate gametes (that is, eggs or sperm) or freeze for future use for the purposes of assisted reproduction; (c) Wear an external condom

Exclusion Criteria:

• Active plasma cell leukemia, Waldenström's macroglobulinemia, POEMS syndrome (polyneuropathy, organomegaly, endocrinopathy, M-protein, and skin changes), or immunoglobulin light chain amyloidosis
• Prior allogeneic transplant within 6 months before the start of study treatment administration or autologous transplant within 12 weeks before the start of study treatment administration
• Live, attenuated vaccine within 4 weeks before the first dose of study treatment
• Central Nervous System (CNS) involvement or clinical signs of meningeal involvement of multiple myeloma. If either is suspected, brain magnetic resonance imaging (MRI) and lumbar cytology are required
• Non-hematologic toxicity from prior anticancer therapy that has not resolved to baseline level or to less than or equal to (<=) Grade 1 (except alopecia, tissue post-RT fibrosis, or Grade < 3 peripheral neuropathy)
• Received a cumulative dose of corticosteroids equivalent to greater than or equal to (>=) 140 mg of prednisone within the 14-day period before the start of study treatment administration
• Prior antitumor therapy in the specified time frame prior to the first dose of study treatment: (Targeted therapy, epigenetic therapy, monoclonal antibody treatment, or treatment with an investigational drug or an invasive investigational medical device or conventional chemotherapy within 21 days, gene-modified adoptive cell therapy or treatment with anti-CD38 directed therapies within 3 months, proteasome inhibitor [PI] therapy or radiotherapy within 14 days, or immunomodulatory drug (IMiD) agent therapy within 7 days)
• Following medical conditions: pulmonary compromise requiring supplemental oxygen use to maintain adequate oxygenation, human immunodeficiency (HIV) infection (participants with a detectable viral load or low CD4 count), active hepatitis B or C infection, active autoimmune disease requiring systemic immunosuppressive therapy within 6 months before start of study treatment, serious uncontrolled ongoing viral or bacterial or systemic fungal infection, cardiac conditions (myocardial infarction <=6 months prior to enrollment, New York Heart Association stage III or IV congestive heart failure, et cetera [etc.])

The data sharing policy of Johnson & Johnson Innovative Medicine is available at www.innovativemedicine.jnj.com/our-innovation/clinical-trials/transparency. As noted on this site, requests for access to the study data can be submitted through Yale Open Data Access (YODA) Project site at yoda.yale.edu