Transmissible gastroenteritis virus (TGEV) is the causative agent of porcine transmissible gastroenteritis, and sensitive detection methods are required for preventing the disease. In this article, reverse transcription-loop-mediated isothermal amplification (RT-LAMP) was developed to detect TGEV. Three pairs of primers targeting the nucleocapsid (N) gene of TGEV were synthesized and used in the RT-LAMP. The optimization, sensitivity, and specificity of the RT-LAMP were evaluated. Our results showed that the RT-LAMP amplified the N gene with high specificity, efficiency, and rapidity at isothermal condition. The optimal reaction condition was achieved at 60°C for 30 min. The RT-LAMP assay was more sensitive than gel-based RT-PCR and PCR. It had a higher sensitivity than enzyme-linked immunosorbent assay (ELISA) using the equal virus templates. In addition, the established RT-LAMP differentiated TGEV from porcine epidemic diarrhea virus, porcine rotavirus, porcine pseudorabies virus, porcine reproductive and respiratory syndrome virus, and avian infectious bronchitis virus. The approach is suitable for detecting TGEV for field diagnostics or in less-equipped laboratories due to its convenience and simplicity.