Simplification of Rational Algebraic Expressions is apparently a challenging task for learners to accomplish. Misconceptions of the mathematical ideas and procedures in this process often lead to learners’ errors. This study aimed to determine the difficulties encountered by Grade 8 Learners in the simplification of rational algebraic expressions using the Modular approach during the pandemic in Zambales, Philippines. The study utilized the quantitative descriptive research design with an item test on simplification of rational algebraic expressions and documentary analysis in gathering data from two hundred participants who were randomly selected. The students were assessed “Right Difficulty” in Simplifying Rational Algebraic Expressions. There is a significant difference in the performance of the students between the two tests on rational algebraic expressions. There is a positively light or weak relationship between the assessment for Simplifying Rational Algebraic Expressions and the level of academic performance. Based on the summary of the investigations conducted and the conclusions arrived at, the teacher may provide an intervention program through cooperative learning or differentiated learning to help and assist students with difficulties and struggle in Simplifying Rational Algebraic Expressions by focusing on the encountered difficulties.