Islamic Education (PAI) plays a strategic role in shaping students' character through teaching the values of tauhid, morality, and life skills in accordance with Islamic teachings. Diagnostic assessment is a crucial step to ensure that students not only understand the material cognitively but are also able to internalize these values in their daily lives. This study aims to describe the implementation of cognitive diagnostic assessment in the PAI subject at SMP Negeri 3 Cikarang Utara, which has implemented the Merdeka Curriculum since 2022, and to describe the implementation of non-cognitive diagnostic assessment in the same subject. The research employs a qualitative descriptive method with data collection techniques including in-depth interviews, observations, and document analysis. The research subjects consist of the school principal, PAI teachers, and students as the primary data sources to obtain a comprehensive overview of the implementation of diagnostic assessments. The findings reveal that cognitive diagnostic assessments are conducted through written tests, group discussions, and analysis-based assignments to measure students’ understanding of Islamic concepts. Meanwhile, non-cognitive diagnostic assessments are carried out through behavioral observations, questionnaires, and interviews to identify students' character, learning motivation, and socio-emotional challenges. The implementation of these diagnostic assessments is considered helpful for teachers in designing more relevant, personalized, and student-centered learning experiences. This study recommends intensive training for PAI teachers to enhance their ability to develop valid and effective assessment instruments. Additionally, better technical support and time management are needed to optimize the implementation of diagnostic assessments, ensuring that holistic learning objectives can be achieved effectively.