Peripheral T cell lymphoma, not otherwise specified (PTCL-NOS) is a heterogeneous subtype of non-Hodgkin's lymphoma. This study aims to better define the prognostic factors and compare the predictive value of the prognostic scores in Chinese patients with PTCL-NOS. One hundred and five patients diagnosed as PTCL-NOS from our institution were retrospectively studied and grouped according to four previously described prognostic scores [International Prognostic Index (IPI), Prognostic Index for PTCL-NOS (PIT), modified PIT (m-PIT), and International PTCL Project (IPTCLP)]. In addition to clinical parameters, peripheral lymphopenia and thrombocytopenia, serum Epstein-Barr virus positivity, and tumor Ki-67 were significantly associated with poor disease outcome. Multivariate analysis revealed that age >60 years, poor performance status, elevated lactic dehydrogenase, and bone marrow involvement were independent adverse variables for survival. All prognostic scores were successful for survival estimation. Risk subgroups in IPI and PIT could be further discriminated by platelet count (IPTCLP factor) and Ki-67 (m-PIT factor), respectively. Together, patient- and tumor-specific characteristics may be incorporated in risk stratification of PTCL-NOS patients. The prognostic scores could be mutually active to improve their predictive value of disease outcome.