During the past ten years combinatorial chemistry developed from a powerful synthetic methodology, providing large libraries of usually simple new chemical entities, to a comprehensive strategy presently covering a multitude of technologies across the whole workflow from hit generation to lead optimization. Thus combinatorial chemistry had a major impact not only on the pharmaceutical research but also with some delay on the agrochemical research. The agrochemical discovery environment is different from that of the pharmaceutical research in that it relies mainly on whole organism screenings. This review summarizes some recent applications of combinatorial chemistry in the agrosciences, covering all the three major fields of research: fungicides, herbicides, and insecticides. The article focuses on libraries with published biological activities and thus highlights some characteristic features of successful agrochemical libraries, which may be fundamentally different from pharmaceutical libraries.