The study aimed to investigate the effect of Effective Comprehension Strategy Instruction (ECSI) on (1) improving the learners’ reading comprehension skills, (2) learners’ mastery learning and (3) teacher’s pedagogical delivery in Grade 4 pupils of Bag-ong Borbon Primary School, Buug, District, Zamboanga Sibugay Division. Quantitative and qualitative methods were both employed in this study. Observations on pupils’ behavior towards the lesson and the results of the formative assessment test through the experimental method were also gathered and used to analyze results. Interviews were also conducted to come up with results for the pedagogical delivery of the teachers. The test was conducted to the eighteen (18) Grade IV pupils and also to three (3) teachers of the school. SPSS software was used to analyze data. T-test was run to determine the effect of the ECSI on improving learner’s comprehension skills. Significant findings revealed that learners who have undergone lessons with ECSI strategy have significantly higher scores than those lessons without ECSI strategy. ECSI is, therefore, an effective strategy to develop learners’ reading comprehension which should be employed by the teachers in the classroom.