Standardized testing is viewed as particularly incompatible to the process of learning due to its summative nature as it measures what students are able to recall and produce. Because of the discrepancy between the process of learning and products of learning, educators today have come to recognize that an alternative form of assessment is required to complement the existing form of assessment. This study intends to determine the techniques ESL teachers use in implementing portfolio as an assessment tool. The techniques ESL teachers employed while implementing the assessment process in the classroom enabled the researchers to propose a model for portfolio assessment. Currently, ESL teachers in Malaysia do not have a specific model or technique to conduct the portfolio assessment process because portfolio is heard of but not widely used. Therefore, this study was carried to scrutinize procedures ESL teachers use as a guide in instructional planning and student evaluation based on their teaching in the L2 classroom. The participants were nine ESL secondary school teachers in Malaysia. Semi-structured interviews, classroom observations and teachers’ individual portfolios were utilized to explore the techniques which served as a guideline for ESL teachers employed for the teaching and learning in the classroom. Findings indicate that the portfolio assessment model developed has provided ESL teachers the opportunity to document individual student’s growth. Furthermore, the teachers divulged that teaching is sustained when teaching materials, teaching techniques and assessment techniques were upgraded to help students in achieving the learning outcomes. The results of the study have implications for assessment, teaching and learning of English as a second language.