Self-knowledge is an important element of metacognition. It encompasses understanding one's own strengths and weaknesses and includes belief and self-assessment of one's capacity to perform a task. Cognitive skills comprise a range of mental processes, such as attention, memory, problem solving, systems thinking, abstract thinking, and critical thinking, that are essential for acquiring and applying knowledge. The research described in this paper examined the ability for self-knowledge and cognitive skills of electronics students engaged in project-based learning. The study, which used quantitative and qualitative tools, involved 140 twelve-grade electronics students and explored the self-knowledge and cognitive skills they exhibited while executing their final projects. The correlation and paired-samples t-test between the students' self-report questionnaire (indirect assessment of cognitive skills) and achievement test (direct assessment of cognitive skills) scores were examined to assess the students' self-knowledge and cognitive skills. The findings revealed a significant difference between self-report questionnaire scores and achievement test scores, indicating that the students' self-knowledge did not reflect their actual low level of cognitive skills. Measuring self-knowledge and cognitive skills in project-based learning is essential for assessing the effectiveness of the learning process, resulting in improved project outcomes and a firmer foundation for future academic and professional success.