A reversible probe based on diketopyrrolopyrrole–tellurophene conjugate for the detection of reactive oxygen species has been designed and synthesized. The probe utilizes the redox properties of the tellurium atom for the detection of reactive oxygen species and exhibits high selectivity and sensitivity towards H 2 O 2 ; the presence of which is demonstrated by a fluorescent signal. In addition to fluorescence signal, the probe displayed a color change from light blue to light purple upon oxidation by H 2 O 2 in aqueous media. The generated tellurophene-1-oxide may be quickly reduced by glutathione to regenerate the original diketopyrrolopyrrole–tellurophene conjugate. The probe can be applied to monitor the concentration of H 2 O 2 in aqueous solution over an approximate pH range 3.8–8.0.