Specifically focusing on class 4 TMI (Tarbiyah Muallimat al-Islamiyah) at the Modern Islamic Boarding School of Al-Ikhlash Female in Kuningan, West Java, the study aims to investigate the potential beneficial impact of portfolio assessment on the learning outcomes of Nahwu lessons for fourth-grade students. The finding that 4 TMI has impetus for this investigation. The target population for the study, which included all fourth graders, was carried out during the odd semester of the 2022 academic year. All students in class 4 TMI were included in the research sample thanks to the saturated sampling method that was used. A quasiexperimental design was used to evaluate the effectiveness of portfolio assessment, with the experimental class implementing portfolio assessment while the control class continued to use the standard evaluation method. The learning outcomes of the students in the control class produced an average score of 71.67. When comparing this score to that of the experimental class, which used portfolio assessment, it become clear that the pupils’ comprehension of the Nahwu material had significantly improved. These results show that portfolio evaluations have a chance to improve fourth-grade students’ learning outcomes in Nahwu.