Background: Peripheral T cell lymphoma (PTCL) is a heterogeneous entity with poor survival. We evaluated the neutrophil-to-lymphocyte ratio (NLR), absolute lymphocyte count (ALC), and platelet count as new prognostic factors for PTCL. Patients and Methods: We retrospectively analyzed 77 patients with PTCL initially treated with anthracycline-based chemotherapy. Survival curves were compared between groups with different initial NLR (iNLR), end-point NLR (eNLR), initial ALC, and platelet counts. Cox regression was used to analyze the risk factor for survival. Results: Patients with a higher eNLR (≥3), lymphopenia (< 1,000/μL), and thrombocytopenia (< 150 K/μL) had an inferior progression-free survival (PFS) and overall survival (OS) compared to their counterparts, while a higher iNLR (≥3) was predictive of a shorter OS but not PFS. Among these, thrombocytopenia was an independent poor prognostic factor for both PFS and OS, with a hazard ratio of 2.42 (p = 0.012) for PFS and 4.21 (p = 0.006) for OS. The presence of thrombocytopenia further stratified patients with a worse prognosis within overlapping risk-groups by the prognostic index for PTCL. Conclusions: Our study showed that thrombocytopenia at diagnosis was an independent prognostic factor for survival in patients with PTCL.