Writing is an important part of communication. It allows one to communicate with a wider audience with greater understanding and simplicity. However, poor writing skills have a significant impact on a student's ability to communicate with others. The writing process itself interferes with learning for a student who is struggling with a writing problem. The purpose of the study was to find out if using the portfolio assessment strategy in terms of reflective journal writing and picture series will be an effective writing strategy in improving writing skills performance in Grade 8 English. Specifically, it was geared towards answering the following questions: 1. What is the frequency and percent distribution of the students’ scores in English Writing? 2. What is the mean pretest score of the respondents before utilizing the portfolio assessment strategy in writing? 3. What is the mean posttest score of the respondents after using the portfolio assessment strategy in writing? and 4. Is there a significant difference in the pretest and posttest of the students in writing before and after using the portfolio assessment strategy in writing? Results revealed that there is a significant difference in the mean pretest and posttest scores of the respondents in writing activities using the portfolio assessment strategy.