Accumulating bodies of evidence indicate that immune dysregulation plays a key role in the development of osteosarcoma (OS). Programmed death 1 (PD‐1) is a surface receptor expressed on activated and exhausted T cells, which mediate T‐cell inhibition upon binding with its ligand. Researches on PD‐1 and OS remain extremely limited. Here, we investigated whether PD‐1 could be involved in the development of OS. Expression of PD‐1 was measured by flow cytometry on peripheral CD4+ and CD8+ T cells from 56 OS cases and 42 healthy controls. Data revealed that percentages of PD‐1 were significantly upregulated on both peripheral CD4+ and CD8+ T cells from OS patients (p < 0.001 and p < 0.001, respectively). Patients with different tumor locations did not present obvious variations in PD‐1 level. However, patients with metastasis showed significantly higher level of PD‐1 on CD4+ T cells than those without metastasis (p < 0.001). Furthermore, PD‐1 expression on CD4+ T cells started to increase in stage III, whereas PD‐1 expression on CD8+ T cells started to increase in stage II. In addition, patients with pathological fracture were observed to have elevated PD‐1 on both CD4+ and CD8+ T cells. These data suggest that PD‐1 is involved in the pathogenesis of OS, especially in the progression of disease.