The Covid-19 pandemic drastically changed the education system and forced schools to adopt the online teaching setup. However, it affects the teachers' workload globally. The study aims to assess the workload level of the 95 teachers at the Technological Institute of the Philippines - Manila during the online setup. Using the NASA Task Load Index assessment tool, the researchers could evaluate the different workload sources. The Analysis of Variance and pairwise correlation analysis was also used so that the researchers could determine if their demographic profile significantly affects their current workload and if the different sources have a significant relationship with each other. After this, the findings revealed an 80.86% on teachers' workload level, which is greater than the level of workload acceptability. The current setup also demands good performance, intense thinking, and effort during the new learning setup. The researchers found that the result is still the same even though they are weighted based on their demographic profile. But there is a very high positive relationship between frustration and temporal demand, the same as between frustration and effort. The relationship between frustration and mental demand and effort and physical demand also shows a high correlation. The recommended practices for the school and teachers are also created to help them ease and reduce zoom fatigue without jeopardizing the quality of education they deliver to the students.