Haptens, bioconjugates, and antibodies for highly sensitive immunochemical analysis of the new-generation fungicide penthiopyrad are described. Two haptens with equivalent carboxylated linkers were prepared, and the purified active esters were efficiently coupled to proteins. The results revealed slightly different antibody-eliciting capacities for the two synthetic derivatives. All of the produced antibodies were specific for penthiopyrad, and showed affinity values in the nanomolar range.