BACKGROUND: In recent years, pyridylpyrazole derivatives, such as pyridylpyrazole-containing anthranilic diamide have attracted much attention by virtue of their useful insecticidal properties and unique action mode. Moreover, some pyridylpyrazole-containing compounds have also been found to possess significant fungicidal activities. With the aim of discovering new bioactive agrochemicals for crop protection, a series of poly-heterocyclic compounds containing pyridylpyrazole and aziridine, or β-lactam, or thiazolinonemoieties were synthesized. RESULTS: A series of pyridylpyrazole-containing poly-heterocyclic compounds were obtained, and confirmed through IR, ¹H NMR, 13C NMR, HRMS and elemental analysis. The crystalline structure of 4-(3-bromo-1-(3-chloropyridin-2-yl)-1H-pyrazol-5-yl)-3-chloro-1-mesitylazetidin-2-one (compound 13f) was determined to further illustrate a trans- configuration of the β-lactam motif. In addition, bioassays showed that most of these new compounds exhibited modest insecticidal activity towards Mythimna separate Walker at 200 μgmL-1. Some of the compounds displayed excellent fungicidal activity towards some plant fungi, including Cercospora arachidicola (13j: EC50 =14.5 μgmL-1), Physalospora piricola (12d and 13d: EC50 =10.5 and 9.70 μg mL-1), Alternaria solani Sorauer (13j: EC50 =7.29 μg mL-1), Puccinia sorghi Schw. (13d: control efficacy 99.0±2.1% at 200 μg mL-1) and Erysiphe graminis (14d: control efficacy 95.0±1.4% at 200 μgmL-1). CONCLUSION: Compounds 12b–12e, 13a, 13d, 13f, 13j, 13 k and 14d could be considered potential fungicidal lead compounds to do further structural optimization. The structure–activity relationship analysis in this study brings some new understanding to the biological activities of N-pyridylpyrazole-containing compounds, and provides important information for the research and development of novel agricultural fungicides with poly-heterocyclic structures. [ABSTRACT FROM AUTHOR]