A novel series of 1 : 1 cocrystals of 2‐cyanoguanidinophenytoin (CNG‐DPH) with primary, secondary, and tertiary aliphatic amines has been presented through this work. The antimicrobial activities of all new CNG‐DPH‐amine cocrystals were studied. The existence of cocrystals has been proven through crystal structure results. The 5‐Oxo‐4,4‐diphenylimidazolidin‐2‐ylidenecyanamide‐piperidine cocrystal (10) is located in an orthorhombic crystal system, and the cocrystal is connected via the N−H−N hydrogen bond between the cyanide group and the piperidine molecule. Hirshfeld surface analysis authenticated supramolecular contacts. Ring puckering analysis revealed a chair stereochemistry at the 6‐membered piperidine. The crystal packing has been stabilized through intermolecular forces, hydrogen bonds, and interactions within the gravity center of rings (Cg). The antimicrobial activities of the newly synthesized compounds were only effective against Gram‐positive bacteria, demonstrating that the antibacterial spectrum of these compounds was restricted. In vitro cytotoxicity of the synthesized cocrystals was assessed in normal cells, giving the highest half‐maximal inhibitory concentration (IC50) ratio (637.63 μg/ml) and the lowest value (181.98 μg/ml).