During an initial Dose Evaluation phase (first 2 cycles) to determine Dose Limiting Toxicities (DLTs), dose combinations of pembrolizumab 200 mg followed by dinaciclib 7 mg/m^2, pembrolizumab 200 mg followed by dinaciclib 10 mg/m^2, and pembrolizumab 200 mg followed by dinaciclib 14 mg/m^2 will be evaluated. Following safety review of the Dose Evaluation Phase, approximately 30 participants each will be enrolled in rrCLL, rrMM, or DLBCL cohorts during the Signal Detection phase. For each disease type objective response rate (ORR) will be determined by disease specific criteria.