Four novel lanthanide La (III), Ce (III), Nd (III), and Dy (III) complexes with (Z)‐4‐(benzo[d]thiazol‐2‐ylamino)‐3‐((benzo[d]thiazol‐2‐ylimino)methyl)‐2H‐chromen‐2‐one (L) were prepared and characterized. The novel compounds' structural compositions were elucidated by the application of analytical and spectroscopic methodologies. From physical and chemical measurements, the general formula for the [LnLCl3]2H2O complexes (C1‐C4) was proposed, which was proven by theoretical measurements. Using cisplatin, gentamicin, ampicillin, and ascorbic acid as standards, the compound's anticancer, antibacterial, and antioxidant qualities were assessed, and activities followed the order: Ce (III)L(C2) > Nd (III)L(C3) > Dy (III)L(C4) > La (III)L(C1) > L where the Ce (III) complexes exhibited the highest activity followed by Nd (III) complexes. Molecular docking studies were performed using the MOA2022 software to identify putative binding mechanisms for the methionine adenosyl‐transferases in liver cancer (PDB ID: 5A19) and the most active site of the Bacillus subtilis receptor (PDB ID: 5e6k), where the strength of the interaction increases with the negative binding energy L ˂ [LaLCl3] ˂ [DyLCl3] ˂ [NdLCl3] ˂ [CeLCl3].