Neurolymphomatosis is the direct endoneurial infiltration of lymphoma cells. Bone marrow biopsy is a widely practiced procedure that is generally considered to be relatively safe. However, bone marrow biopsy can also result in pain and long-term consequences such as nerve injury. Here we report a case of a 68-year-old male who presented with lumbosacral plexopathy due to neurolymphomatosis that was superimposed on a probable traumatic lumbosacral plexopathy mostly involving the sciatic nerve immediately after a bone marrow biopsy.