This study explored the relative effect of student- and teacher-centered instruction on EFL freshmen's affect (anxiety, motivation, attitude, autonomy, self-efficacy and beliefs about English and its learning) and achievement. Two classes of English department freshmen at Shaqra University, KSA participated in the study. Students in the two classes completed a questionnaire probing the target affective variables. An independent t-test proved that the two classes were homogenous in affective variables before the treatment. The treatment class was taught according to student-centered instruction for an academic year. The control class was taught the same courses according to the conventional teacher-centered instruction. The students completed the questionnaire probing their affect. A composite mark of final exam marks of three courses was used as an index of achievement. Analyses of independent sample t-test proved that the treatment class outperformed the control class in all affective variables (except for instrumental motivation) and achievement.