A sensitive and rapid method for the detection of bisphenol A (BPA) using general pH meters or pH paper was developed. Aptamer‐functionalized Fe3O4 magnetic nanoparticles (MNPs) were synthesized to capture BPA in samples, and gold NPs (AuNPs) were modified with acetylcholinesterase and the complementary strand of BPA aptamer. The specific detection of BPA was realized using the combination of BPA‐responsive, aptamer‐cross‐linked MNPs‐AuNPs complex. As the acetylcholine was hydrolyzed to choline and acetic acid, the pH of the solution decreased. The resulting pH change could be measured in real‐time using a pH meter. The sensitivity of detection of this assay was 5 pg/mL with the range of 0.01 to 1000 ng/mL. The pH change could be determined with the naked eye from the color change of a pH indicator strip. This sensor technology is promising and reliable for rapid, sensitive, and on‐site monitoring of BPA in water samples.