The manner schools taught changed from face-to-face to online delivery due to the Covid-19 pandemic. But learners perceived online lessons burdened mental and psychological health, ability to learn, and literacy in reading, writing and arithmetic. Conversely, local studies deemed learners’ ability to succeed in classes improved from moderate pre-pandemic to high during. This study described the sources of self-efficacy, which are mastery experiences, vicarious experiences, verbal persuasion, and physiological feedback of STEM students at NU Fairview Incorporated, were utilized as respondents. As a result of the study, it is showed that the source of their self-efficacy were their mastery experiences which are attributed to frequent engagement in activities and success experiences. It is also found out that there is no significant difference between the sources of self-efficacy and STEM students’ GWA. On the other hand, perceived self-efficacy vary between male and female. Also, vicarious experiences appear to vary on perceived self-efficacy across different specialization within STEM. Findings call for improving teachers’ practices in giving positive feedback on the learners’ output and performance in class. In addition, the need to improve on constructing written works, and activities which are time-bound, and meaningful which intends to encourage and not to exhaust students.