Abstract Novel and efficient multi-SO3H functionalized mesoporous polymeric solid acid (PD-En-SO3H) was synthesized from sulfonation of ethylenediamine (En)-functionalization of mesoporous polydivinylbenzene (PD). The catalyst was characterized by XPS, FT-IR, N2 adsorption-desorption, TEM, SEM, TG and elemental analysis. Characterizations suggest that PD-En-SO3H possess abundant mesoporosity, high BET surface area (369.00 m2/g) and high acidity (2.10 mmol/g). The catalytic activity was investigated for biodiesel (BD) production by esterification of various free fatty acids (FFAs) and synthesis of levulinate esters (BD additive) from fructose. The effects of reaction conditions such as reaction temperature, reaction time, molar ratio of methanol to oil and catalyst amount on conversion of oleic acid were also explored. Interestingly, PD-En-SO3H showed excellent catalytic performance, which was more active than commercial Amberlyst 15 and Nafion NR50. Moreover, it could be reused for four times and still maintained high catalytic activity.