► A monoclonal antibody specific to Sudan red I was produced. ► A rapid strip assay for Sudan red I has been developed. ► A detection limit of Sudan red I in food samples was 10ng/g. ► Strip assay results agreed well with those of a HPLC method. A semiquantitative dip strip assay was developed using nanocolloidal gold-labelled monoclonal antibody (Mab) 8A10 for the rapid detection of Sudan red I in food samples. A protein–Sudan red I conjugate was coated on a nitro cellulose membrane strip in a defined test line. In flow of the complex of nanocolloidal gold labelled-Mab and Sudan red I along the strip, intensive red colour that was formed in the test line reflected the Sudan red I concentration. The test required 10min and had a visual limit of detection of 10ng/g Sudan red I in tomato sauce and chilli powder samples. The results of the strip assay agreed well with those of a high performance liquid chromatography method for both spiked and real commercial samples. The strip was stable for at least 2months at 4°C. The strip assay offers the potential as a useful rapid and simple method for screening of Sudan red I in food samples.