T lymphocytes play central roles in adaptive immunity. Lycium barbarum L. (L. barbarum), also known as wolfberry, is a Chinese herbal medicine with various biological activities, such as enhancing immunity, protecting liver damage, and reducing the side effects of chemotherapy and radiotherapy. Here, we report that polysaccharide-protein complex from L. barbarum (LBP) is able to activate T cells. LBP was isolated from L. barbarum and separated to five homogenous fractions, designated LBPF1, LBPF2, LBPF3, LBPF4, and LBPF5. We found that LBP, LBPF4, and LBPF5 significantly stimulated mouse splenocyte proliferation. The proliferation proved to be of T cells, but not B cells. Cell cycle profile analysis indicated that LBP, LBPF4, and LBPF5 markedly reduced sub-G1 cells. LBP, LBPF4, and LBPF5 could activate transcription factors NFAT and AP-1, prompt CD25 expression, and induce IL-2 and IFN-gamma gene transcription and protein secretion. LBP (i.p. or p.o.) significantly induced T cell proliferation. Our results suggest that activation of T lymphocytes by LBP may contribute to one of its immuno-enhancement functions.