The study examined the interrelationships among personality factors, academic emphasis, studentslecturers relationship and academic achievement orientation of Nigerian undergraduates in Southwest Nigeria. Three thousand four hundred and eighty-nine (3489) randomly selected undergraduates took part in the study. Four (4) valid and reliable instruments were used for data collection. These instruments are: The Big Five Inventory by John and Srivastava (1999); Achievement Goals Orientation Scale by Was (2006); Academic Achievement Motivation Scale by Vallerandet al., (1992); and Student-Instructor Relationship Scale by Creasey, Jarvis, K Adj. R 2 = .359; F(1, 3486) = 19.507; P < .05). Also, students’ personality was found to significantly influenced by academic emphasis of the school (Adj. R 2 = .226, F (6, 3482) = 18726) while students-lecturers’ relationship (Adj. R 2 = .311, F (7, 3481) = 21.788) and undergraduates’ achievement goal orientation (Adj. R 2 = .103, F (6, 3483) = 16.174) were found to be influenced by personality factors. Findings of the study further indicated a significant influence of academic emphasis on undergraduates’ achievement goal (Adj. R 2 = .177, F (1, 3487) = 12.963, P < .05), while students-lecturers’ relationship was also found to influence students’ achievement goal orientation significantly (Adj. R 2 = .159, F (3, 3485) = 16.174, P < .05). The study concluded that the accurate prediction of undergraduates’ academic achievement through personality factors, students-lecturers relationships, and academic emphasis has important implications for education, and not just at the higher institution’s level