In the present work, Acid Red 1 (AR1) dye degradation by two heterogeneous Fenton catalysts, namely iron loaded rice husk biochar (Fe-RHB) and coir pith biochar (Fe-CPB) are studied. Biochar prepared from RHB and CPB were sonicated in the presence of ferric nitrate for the synthesis of Fe-RHB and Fe-CPB by incipient impregnation method. Effect of operational parameters such as pH, the dosage of catalyst, H2O2 concentration and temperature were examined. Characterization of the synthesized Fenton catalyst, Fe-RHB and Fe-CPB were analysed by SEM, EDS, XRD and XPS techniques. In Fe-RHB Fenton system, maximum dye removal efficiency of 97.6% and TOC removal efficiency of 84.2% were obtained at pH 3 for 50 mg L−1 of AR1 concentration, with 16 mM of H2O2 and 5 g L−1 of catalyst dosage within 120 min reaction time. Similarly, for Fe-CPB, maximum dye removal efficiency of 99.1% and TOC removal efficiency of 86.7% were obtained with 16 mM of H2O2 and 4 g L−1 of dosage for 50 mg L−1 of initial dye concentration at pH 3. The prepared catalysts can be reused for successive cycles as the catalyst materials are highly stable and have very less iron leaching property. Display omitted •Iron impregnated biochars are effective heterogeneous Fenton catalyst.•Almost complete decolourization and >85% mineralization efficiency were observed.•Prepared catalysts are highly stable and reusable.