Here, we describe a uracil-DNA glycosylase (UNG)-treated reverse transcription loop-mediated isothermal amplification (uRT-LAMP) for the visual detection of all subtypes of avian influenza A virus (AIV). The uRT-LAMP assay can prevent unwanted amplification by carryover contamination of the previously amplified DNA, although the detection limit of the uRT-LAMP assay is 10-fold lower than that of the RT-LAMP without a UNG treatment. To the best of our knowledge, this is the first successful application of deoxyuridine triphosphate/UNG strategy in RT-LAMP for AIV detection, and the assay can be applied for the rapid, and reliable diagnosis of AIVs, even in contaminated samples.