Portfolio assessment has been implemented in many core disciplines for quality assurance and consistent assessment of learner outcomes. For English language learning, for which varying proficiency levels of learners exist, portfolios are suggested to assess individual learners' progress. The current study was carried out in an online English language course at a higher education institution in Turkey. After the portfolio implementation, the researcher collected learners' perceptions regarding it as an assessment tool through open ended questions. The findings indicated that learners had very positive feelings towards portfolio use in the course because it helped them to see how they were using the target language. They were able to reflect on what they learned, acquired ownership of their work, and took responsibility of their learning process with enthusiasm and enhanced motivation towards the online English language course.