Introduction: Since self-efficacy is a belief about one's capability in doing something successfully or unsuccessfully and it relates to academic achievements directly and indirectly. The understanding the sources of one's self-efficacy could assist that person to achieve a better result in learning or doing something, or, at least, to minimize a reflection from negative sources that could decrease his/her self-efficacy. This study investigated the sources of self-efficacy of English language learners with different genders, nationalities, types of study program, and fields of study. Method: This study used stratified random sampling to draw 480 first-year students at a university to complete a questionnaire. Then, the data was analyzed by descriptive statistics, t-test, and One-Way ANOVA. Results: The result showed slight differences in sources of self-efficacy between learners with different nationality and types of program. Findings revealed that vicarious experience became the highest ranked source for positive self-efficacy while mastery experience was the highest for the negative self-efficacy. Social persuasion was the least influential source regardless of their differences. Discussion and Conclusion: The implications are that teachers and administrators could use the results of this study to develop the strategies to implant positive self-efficacy that results greatly in students' learning process, and to lead their students with those individual differences to be autonomous learners.