Sulfamethoxazole (SMX) has numerous adverse effects and is present in various water systems; thus, the development of a rapid and accurate analytical method to detect SMX in water systems is crucial for protecting the environment and human health. A sulfamethoxazole molecularly imprinted photonic polymer (MIPP‐SMX) capable of facile naked‐eye recognition of target molecules was synthesized using the dual‐functional monomers acrylamide and methacrylic acid. The color of the MIPP‐SMX changed from green to blue in water samples containing sulfamethoxazole (SMX) in the concentration range of 0.5–5.0 mM. Furthermore, a linear correlation existed between the detected Bragg diffraction peak shift Δλ and SMX concentrations in water ranging from 0.5 to 2.0 mM. The detection limit for SMX was 0.3 mM. A recovery rate of 91.9%–108.5% was achieved when the polymer sensor was used to detect SMX in river water samples, with a relative standard deviation of 4.9%–6.0%. The designed MIPP‐SMX enabled rapid visual detection of SMX in water samples. The proposed method represents a significant advancement in the visual detection of SMX in environmental water samples.