To discover more effective antifungal agents, twenty N‐(1H‐pyrazol‐5‐yl)nicotinamide derivatives were designed, synthesized, and structurally confirmed by 1H‐NMR, 13C‐NMR, and ESI‐MS. All target compounds were evaluated for their antifungal activities by mycelia growth inhibition. Preliminary screening results displayed that many of these compounds had good fungicidal activity to S. sclerotiorum and V. mali. Compound B4 exhibited antifungal activity against S. sclerotiorum and V. mali with EC50 values of 10.35 and 17.01 mg/L, respectively. The experiment in vivo identified that compound B4 was effective for suppressing rape sclerotinia rot caused by S. sclerotiorum at 50 mg/L. The molecular docking study and scanning electron microscopy preliminary clarified the possible antifungal mechanism of compound B4.