Strategies about addressing Least Mastered Skills of the students are necessary because of the effect of Covid 19 Pandemic. Many schools are subscribing to different platforms to maximize the time they must implement the curriculum and address the least mastered skills brought by pandemic and other classes interruptions. The study sought to assess the effect of Scaffolded Technology-assisted Asynchronous Activities to address the Least Mastered Skills of SBUR SHS students in Earth and Life Science. Based on the results of the 1st quarter exams in Earth and Life Science, most of the students of SBUR got very low scores in the topic Minerals and Rocks wherein majority of the students got the wrong answers consisting of 11 items. These items were considered by the researchers as Least Mastered Skills. An intervention called Scaffolded Technology-assisted Asynchronous Activities was developed following the Scaffolding Framework by (Hattie, 2019) consisting of modeling, guided practice, and independent practice. The intervention was developed by the researcher and the science teachers of San Beda University Rizal (SBUR). After the validation process, it was given to the students who are taking Earth and Life Science subject and were given two weeks to complete the activities. After two weeks, students were given a Post Test parallel to the test they encountered during the 1st quarter examination. Students who have not completed the intervention activities are not considered as participants of the study. The mean percentage of 11 items of the Least Mastered Skills is 0.33 while the mean percentage of these items during the Post Test is 0.54. When paired-sample T Test is used, the computed value is 0.003 which is lower than the critical value of α=0.05, which means there is a significant difference between the scores in the 1st quarter exams and the Post Test results of the participants. This implies that the Scaffolded Technology-assisted Asynchronous Activities are effective in addressing the Least Mastered Skills of SBUR SHS students in Earth and Life Science.