This study seeked to identify the factors affecting students’ performance of the ELT program who are taking advanced English during the period 2017-2 at Universidad Industrial de Santander in Bucaramanga, Colombia. The study was carried out with 40 students from three different groups. The means of data collection were: a questionnaire of 38 likert scale questions categorized into 4 factors (linguistic, psychological, social and curricular). Additionally, a group interview with one open question was conducted with 4 of the 40 participants mentioned above. The questionnaire and interview findings revealed that the most influential factor regarding the syllabus course category was ‘not having high qualified teachers’ while in the psychological perspective category was ‘not working under pressure’. Concerning the linguistic classification, the most remarkable factor was ‘oral fluency’ whereas ‘peer interaction’ was perceived as the most important factor within the social context category. In brief, within the four proposed categories, the syllabus course was the most affecting section since students indicated that nine out of its ten factors affected their English proficiency level. On the contrary, because there were only three affecting aspects in the psychological section, it is the one that had the least impact on the students’ proficiency level.