Biochar is a carbon-rich product generated from the incomplete combustion of biomass through pyrolysis. Biochar plays an important role in removing pollutants from the environment. In this study, biochars were obtained from peanut shell agricultural waste by the limited-oxygen method at 300, 500, and 700 °C. The adsorption capacity of imidacloprid onto the biochar was increased with the increasing pyrolysis temperature. The solution temperature and biochar dosage had positive effects on the adsorption of imidacloprid. The adsorption capacity of the biochar on imidacloprid was increased with the increasing of pH in acid and neutral solution but slightly decreased in weak base solution (pH 9). An analysis of adsorption kinetics showed that the adsorption of imidacloprid on the biochar perfectly followed pseudo-first-order and pseudo-second-order models with R2 coefficients above 0.97. Furthermore, the Langmuir and Freundlich models highly correlated with the sorption isotherm data. In summary, this study confirmed that peanut shell biochar is an efficient adsorbent for the removal of the pesticide imidacloprid.