This is a non-randomized, open-label study evaluating the safety and efficacy of pembrolizumab (MK-3475) used in combination with dinaciclib (MK-7965) in the treatment of relapsed or refractory chronic lymphocytic leukemia (rrCLL), multiple myeloma (rrMM), or diffuse large B-cell lymphoma (rrDLBCL) in up to 138 participants from multiple sites.