Airfoil with leading edge tubercles reported in the literature for its potential outcomes in improving aerodynamic performance by mitigating separation and delaying the stall. Counter-rotating vortex pairs (CRVPs) have the potential to impede the steady airflow over wings, reducing lift and increasing drag. These vortices cause turbulent airflow, which lessens the ability of the wing to produce lift. In the present study, surface flow visualisation is carried out using photo luminescent technique for the flow over a NACA0020 airfoil modified with sinusoidal tubercles at the leading edge. The experiments carried out in a wind tunnel for a velocity of 10 m/s which is at Reynolds number 140,000 subjected to 0°, 5°, 10°, 15°, and 20° angles of attacks. Test models are fabricated using the 3D printing technique with a sinusoidal tubercle geometry of 16.5 mm wavelength and with a different amplitude of 1.65, 4.38, and 9 mm. Results emphasized the CRVPs are formed with a larger size as the amplitude decreases. The flow structures are moved significantly towards the leading edge for low amplitude 1.65 mm case as compared to the higher amplitude 9 mm geometry as the angle of attack is increased.