A female patient with end-stage chronic obstructive pulmonary disease received a double-lung transplant from a donor with serologic evidence of past syphilis. The recipient showed a Treponema pallidum-specific IgG seroconversion 8 days after transplantation with increasing titers at follow-up. In Month 3 post-transplantation the immunoglobulin G (IgG) antibody titer decreased. Retrospectively, we argue that the reactive syphilis serology in the recipient was due to a transmission of immunocompetent B cells in the graft rather than a transmission of T pallidum.