English has become a key subject of educational systems worldwide. Thus, researchers have centered their attention on psychosocial processes that influence English proficiency in EFL settings. The aim of our study was to investigate the relation between affective variables, motivation and proficiency and assess which attitudinal/motivational domains can better predict English proficiency. Mini AMTB and English Proficiency test were employed to a sample of 354 university students. Our findings showed that students' achievement was significantly associated with their motivational intensity, their attitude towards learning English and their desire to learn it, as well as with their opinion of English native speakers and their perception of the quality of the English course. Secondly, instrumental orientation, motivational intensity, attitude towards learning English, and students' perception of the quality of the English course were found to be the predictors of achievement. Thus, creating a culturally enriching in-class environment based on student-centered strategies could impact on pupils' proficiency more than teachers' teaching abilities and in-class attitude.