Aeromonas hydrophila is ubiquitous in the aquaculture industry and a constant cause of severe disease and economic losses. The early diagnosis of these infections is crucial for disease surveillance and prevention. We developed a real‐time recombinase polymerase amplification (real‐time RPA) assay for detection of A. hydrophila using the haemolysin gene. The assay was performed at 37°C for 20 min and was highly specific with no cross‐reaction with other fish pathogens or with other Aeromonas species. The assay detection limit was 102 copies of the Aeromonas hydrophila per reaction. Compared with traditional culture‐based method or real‐time PCR, the diagnostic sensitivity and specificity of the real‐time RPA were 73.7 and 100%, as well as 64.7 and 93%. Our newly developed real‐time RPA was specific and sensitive and can be used in large‐scale and point‐of‐care field investigations of A. hydrophila infections to enable earlier diagnoses.