This study was designed to investigate the determinant factors affecting academic performance of regular undergraduate students of Arba Minch University (AMU) Chamo Campus students. The study employed the use of correlation design to establish the nature of the relationships. Data were collected from 100 respondents selected from all the 12 departments of Arba Minch University Chamo Campus students using the stratified sampling method. To analyze the data, the Pearson product moment correlation statistical tool and econometrics data analysis (OLS regression) method were used with the aim of establishing the relationship between factors related to student's background and family background on academic performance of regular undergraduate students at Arba Minch University Chamo Campus students. The findings revealed the existence of a significant relationship between gender difference, university entrance exam and studying hours and academic performance (CGPA). The findings also revealed that there was a significant relationship between students former academic back ground, studying hours, and student's behavior on taking of alcoholic drug and chat on academic performance of students. On the basis of the findings, the researcher recommended that emphasis should be taken to improve the academic performance of female students and improving students' performance earlier before the joined in to university.