This study shows the assessment of mental workload for jeepney drivers in Tanay, Rizal. This aims to observe the bottleneck and evaluate jeepney drivers’ circumstances that affect their mental workload and identify the factors influencing the mental workload of the jeepney drivers while on duty. The researchers applied the Slovin’s Formula in order to get the correct sample size appropriate for the study. The mental workload of the jeepney drivers was assessed through the use of NASA-TLX (National Aeronautics and Space Administration Task Load Index) with six subscales such as mental demand, physical demand, temporal demand, performance, effort, and frustration. The six step measurements in NASA TLX were also used in this study, i.e., weighting, provision rating, scoring, weighted workload (WWL), weighted workload score, and scoring interpretation. In accordance with the gathered data, the research shows that the indicator physical demand (PD), with a score of 351.46, which is in the very high category on the scale, is the most dominant factor among all the other indicators, and frustration level, with a score of 98.33, will be the least contributor factor among the remaining five indicators. Furthermore, the one-way analysis of variance (ANOVA) was used by the researchers to compare the means of two or more independent variables and to see if there is statistical evidence that the related population means differ significantly. Findings conclude that physical demand is the most prominent among all the indicators and the leading contributor to the mental workload of the jeepney drivers that drive trips along the Tanay-Siliuan route.