The chalcone derivatives or 1,3-diphenyl-2-propen-1- ones are known for their multiple anti-infective activities, they may prevent or delay inactivation, degradation and excretion of anti-infective drugs. The wide variety of pharmacological activities reported for these compounds include antimalarial, anti-inflammatory, cytotoxic, anticancer, and antioxidant properties etc. The imidazopyridine nucleus and like chalcone derivatives possesses many anti-infective properties including antibacterial, antiviral, antiprotozoal,anthelmintic. Similarly, imidazo pyrimidine nucleus possesses important therapeutics such as calcium antagonists, anticancer agents, antifungal activity anti-inflammatory and analgesic activity. The present paper describes the synthesis of new chalcones carrying this imidazopyridine/imidazopyrimidine heterocyclic core from commercially available 2-aminopyrimidine and 2-aminopyridine as starting materials. The chalcones (4a-4f and 10a -10f) thus derived (Scheme 1 and Scheme 2) have been evaluated for their antimicrobial activities against Escheria.Coli, Pseudomonas.aeruginosa, Staphylococcus.aureus and Streptococus .pyogenes, while using Ciprofloxacin as the reference drug (Table 1). In general it is observed that imidazo[1,2-a]pyrimidine chalcone (4a, 4b, 4c, 4e and 4f) derivatives showed excellent activity to good activity when compared to imidazo[1,2-a] pyridine chalcone derivatives (10a – 10f) towards the tested bacterial strains.