This paper relates the synthesis and study of the antifungal activity of azachalcone derivatives (I) and (II). The synthesis of azachalcone (1,3-di(pyridin-2-yl)prop-2-en-1-one) by classical method did not allow to obtain the desired product. Condensation of 2-acetylpyridine with sodium carbonate-catalyzed 2-formylpyridine in aqueous medium has been shown to be effective to produce azachalcone. The products I and II were obtained by performing the condensation reaction both in the basic catalysis and in the presence of HCl(c.) in alcohol. The mechanism of formation of the product (I): the Claisen-Schmitd condensation and Michael addition generates the diketone intermediate, which participate in the aldol double reaction with the third molecule of 2-acetylpyridine (Fig. 1, I). The mechanism of formation of the product (II) from azachalcon and the diketone intermediate present in the reaction medium was confirmed by direct synthesis of the product from the starting substances obtained subsequently as a result of Michael addition, followed by intramolecular condensation and subsequent cyclisation (Fig. 1, II). For the characterization of the final and intermediate products FTIR, 1H-NMR, 13C-NMR spectroscopy were used. The structure of compounds I and II was confirmed by X-ray diffraction on the monocrystal (Fig. 1, I and II). Conclusion: For compound (I) the minimal bacteriostatic and fungicidal concentration are within the limits 0.125-1.0 mg/mL and for compound (II) the minimal bacteriostatic and fungicidal concentration are in the range 0.0039-0.5 mg/mL.