Studies of pharmaceutical drug/active pharmaceutical ingredient (API) compatibility represent an important phase in the design or development of new formulation stage and drug delivery systems. Excipients in the formulations influence the chemical nature, stability, manufacturability, drug bioavailability or delivery of the drug to the patient. Acetyl Salicylic Acid (ASA) is one of the most widely used analgesic, which is poorly soluble in water and causes gastrointestinal irritation. Its cocrystal with Lysine (1:1 part by weight) were prepared in 50% aqueous ethanol and evaluated for Scanning Electron Microscopy, FT-IR spectra, X-ray diffraction, Differential Scanning Calorimetry and in vitro dissolution study. Acetyl Salicylic Acid-Lysine cocrystal were found to be disc shaped with rough surface in SEM, drug content in the complex was found to be 60% DSC thermograms PXRD and FT-IR confirmed the formation of the cocrystal. Solubility of the prepared cocrystal was found to be improved, ASA-Lysine cocrystal showed 96.62% release at 5 minutes and pure ASA showed 96.62% release at 120 minutes and commercial aspirin showed 96.62% release at 60 minutes at PH 4 acid buffer. It was concluded that ASA-Lysine in definite proportion by weight may be of potential use for improving the solubility of ASA and hence its bioavailability..