This study presents detailed microstructural investigations on single and bilayer thin films of two medium entropy alloys (MEAs) synthesized using magnetron sputter deposition. Single layer thin films of CoCrFeNi and AlCoCrFe show single-phase face-centered cubic (fcc) and body-centered (bcc) structure, respectively. The bilayer thin film consisting of CoCrFeNi (fcc) and AlCoCrFe (bcc) has a sharp interface between them with an equiatomic composition. Nanodiffraction was used to characterize planar defects in the fcc films. This first study on bilayer film of two MEAs is transformative to other systems and will help fundamental studies on high entropy alloys.