This study was performed to figure out the relationship between undergraduate students' 21st-century skills (21CSs), physics academic achievements, attitudes towards physics, and perceptions of physics teaching and learning. The study was carried out with 329 undergraduate students who had taken physics courses from Architecture-Engineering, Education, and Health Sciences Faculties. For collecting data of the study, "Scale of Attitude towards Physics", "Scale of Perception Related to Physics Teaching and Learning" and "Malaysian 21st-Century Skills Instrument" which had adapted into Turkish, were applied to the undergraduate students. Before conducting statistical analysis, the homogeneity and normality tests were applied to the obtained data. All descriptive data of the study which collected using on-line questionnaire form were analyzed by frequency, mean, and percentage. The relationship between variables was analyzed using multiple linear regression testing, as well. Based on the statistical analysis carried out on the obtained data, significant relationship wasn't found between the 21CSs of undergraduate students and their physics success. Contrary to this result, a significant relationship was determined between undergraduate students' 21CSs and their attitudes toward physics, and their perceptions related to physics teaching and learning. Since positive attitudes and perceptions towards physics have positive effects on physics course success, it can be stated that undergraduate students' 21CSs indirectly affect the physics success of undergraduate students.