Abstract Many bio‐based polymers made from natural resources do not show satisfactory biodegradability, leading to micro‐plastic pollution. Here, thiol‐ene click polymerization of di‐3‐butenyl l ‐malate (BMA) and diallyl l ‐malate (AMA) with several dithiols including 1,8‐octanedithiol (OD) proceeded at 80 °C to give poly(ester‐thioether)s in excellent yields (70 %–90 %). Using an azo‐type radical trigger, polymerization proceeded more rapidly to give the expected poly(ester‐thioether)s with M n ranging from 1.9×10 3 to 9.4×10 3 and a molecular dispersity index ( M w / M n ) of 2.1 9 –3.6 6 . Click polymerization using 1,2‐ethanedithiol (ED), ethylene bis(thioglycolate), and 2,3‐butanedithiol proceeded to give similar poly(ester‐thioether)s. In differential scanning calorimetry, all samples except for poly(BMA‐ alt ‐OD) had single T g values between −37 and −47 °C. In biodegradation tests using activated sludge, poly(BMA‐ alt ‐OD) and poly(AMA‐ alt ‐ED) hardly showed biodegradability, but the other poly(ester‐thioether)s showed 13 %–22 % biodegradation after 28 days. Our results open up new avenues in the design of bio‐based polymers to reduce micro‐plastic pollution.