A positive correlation between self-esteem and academic achievement is often noted in the literature on educational psychology. As such, self-esteem and academic achievement are often inter-related. Additionally, gender is believed to have an impact on an individual’s self-esteem and varied disparities are found in self-esteem level between genders. The relationship between self-esteem and academic achievement among undergraduates in Malaysia, is still understudied and the lack of literature necessitates an empirical study. Hence, this study explored the relationship between self-esteem and academic achievement among undergraduates of a private university in Malaysia. Also, it investigated if there is any significant difference in self-esteem and academic achievement between genders. A convenience sampling method was employed on 60 male and 60 female undergraduates of TESL (Teaching English as a Second Language) program. The Rosenberg Self-Esteem Questionnaire was utilized to obtain the data on the participants’ self-esteem and their Grade Point Average (GPA). Data analysis using Spearman’s rho correlation revealed a significant relationship between self-esteem and academic achievement. Based on the Chi-square test result, a significant difference in academic achievement between male and female students was established. However, the independent t-test result revealed an absence of significant difference in self-esteem between male and female students. The findings demonstrate essential implications for students, counselors, and educators, and suggest relevant recommendations for future research. A larger sample size should be employed, and other important demographic variables should be explored to examine more in-depth into this interesting field of study.