The idiotypic protein expressed by B lymphoma cells is a clone‐specific tumor antigen which may be suitable for immune targeting by T cells. In this study, we cloned the immunoglobulin heavy chain variable gene (VH) of the idiotypic protein from a patient with B cell lymphoma and used a synthetic peptide of 22 amino acids corresponding to the VH complementarity‐determining region (CDR)‐3 of the idiotypic protein to investigate whether autologous T cells could recognize this unique peptide. We demonstrated that autologous T cells possessing both CD4⁺ and CD8⁺ phenotypes could be propagated. The T cells were able to proliferate, secrete cytokines, and lyse autologous cells presensitized with the specific peptide in a major histocompatibility complex‐dependent manner. Moreover, these CDR3 peptide‐primed T cells were also able to kill autologous lymphoma cells. Our results therefore offer new perspectives for specific therapeutic vaccination for the treatment of B cell lymphoma.