Paraneoplastic neurological syndromes (PNS) are often characterized by the presence of antineuronal antibodies in patient serum or cerebrospinal fluid. The detection of antineuronal antibodies has proven to be a useful tool in PNS diagnosis and the search for an underlying tumor. Here, we describe three patients with autoantibodies to several epitopes of the axon initial segment protein tripartite motif 46 (TRIM46). We show that anti-TRIM46 antibodies are easy to detect in routine immunohistochemistry screening and can be confirmed by western blotting and cell-based assay. Anti-TRIM46 antibodies can occur in patients with diverse neurological syndromes and are associated with small-cell lung carcinoma.