This study aimed to examine university undergraduate’s level of Smartphone Addiction (SA) and to investigate the impact of SA on their Academic Performance (AP) with the mediating effect of Technology-Driven Multitasking behaviour (TDMT). The study employed a cross-sectional survey design, with data gathered from 315 university students. The scope is limited to management undergraduates in Sri Lanka. Descriptive and inferential analysis was used while regression analysis was applied to test hypotheses. Further, the Sobel test is used to test the mediate effect in the relationship between Independent Variable (IV) and Dependent Variable (DV. The study put forth that university students were highly addicted to the use of smartphones. SA negatively impacts AP while TDMT also negatively impacts DV. Further, TDMT mediates the relationship between IV and DV. This study suggests that the students should reduce the intense use of smartphones for smoothly doing their academic activities.