The study examined the perceptions of lecturers on the effects of English for specific purposes (ESP) on learner academic proficiency in Nigerian universities, using primary data sourced from a field survey in three selected Nigerian universities. The study was based on the ESP framework and the researcher set an acceptance criterion value of 2.5 for the study. The researcher combined structured interviews and a questionnaire to obtain data from respondents who are all lecturers in Nigerian universities. The data were analyzed with the Likert scale and other statistical tools such as mean, simple percentages and significant ratios. The study calculated a weighted mean value of 3.02 and found that 92% of the respondents to the interviews identified various ESP language skills as significant factors in enhancing student academic proficiency. Based on the weighted mean value of 3.02 which is greater than the acceptance criterion value of 2.5, the study observed that to a large extent, ESP has positive effects on academic proficiency of students in Nigerian universities. Following these findings, the study concluded that ESP enhances the performance of undergraduates in their chosen courses of study. It therefore recommended, among others that ESP should become part of compulsory courses in various departments as a way of improving academic proficiency of students in their chosen courses of study.