In this paper, the dissimilar joining of Poly Lactic Acid (PLA) with Cork Wood (CW) particles reinforced Poly Lactic Acid (CW/PLA) was made by using an Ultrasonic Welding (UW) process. The single lap joint was made to analyse the better joining with good adhesion between the neat polymer and Cork PLA polymer composite. The objective of this study is to formulate a good bonding of neat biodegradable polymeric material with Cork wood particles reinforced composite with concern to the UW factors like Ultrasonic Amplitude (UA), Welding Pressure (WP), and Welding Time (WT). The experimental trial was carried out by altering the levels of UW factors such as UA (25, 28 and 31 µm), WP (0.10, 0.15 and 0.20 MPa), and WT (1, 1.3 and 1.5 sec) with respect to attainment the higher lap shear strength. The statistical optimization methods, including Taguchi and Analysis of Variance, are employed to identify the optimum factors for the welding process and evaluate the proportional impact of the UW factors. The results revealed that the UA of 28 µm, WP of 0.15 MPa, and WT of 1.5 sec exhibits the higher lap shear strength of 24.16 MPa. For the optimized condition, the interface hardness was measured using the Shore D hardness method. The results imply that the maximum interface hardness of 75 was observed at the weld centre. Fractured samples clearly show that interfacial failure is absent, this dictates the weld regions are strong enough to hold the applied load. The developed regression model for the present UW process on the PLA and Cork wood PLA composite is significant and has an R2 value of 92.8%. So, the developed model is suitable for converting into large-scale industrial production and applications.