This study aims to investigate the predictive power of personality traits for EFL students' preference for isolated or integrated form-focused instruction (FFI). Participants were 160 Iranian EFL university students. Results indicated that students' personality traits, as measured by Costa and McCrae (Revised NEO Personality inventory (NEO-PI-R) and NEO Five-Factor Inventory (NEO-FFI) professional manual, Psychological Assessment Resources Inc., Odessa, FL, 1992) NEO-FFI, were significantly related to students' preference for isolated or integrated grammar instruction as assessed by Student Preference for Grammar Instruction Questionnaire developed by Spada et al. ("System," 37(1):70-81, 2009). Multiple regression analyses indicated that NEO-FFI variables of extroversion, agreeableness, and open to experience were significant positive predictors of EFL students' preferences for integrated FFI while neuroticism had a negative relationship with that. Furthermore, NEO-FFI variables of conscientiousness and neuroticism were significant positive predictors of students' preferences for isolated FFI while extroversion and open to experience had a negative relationship with it. The results were discussed and the implications were made with regard to individual differences in educational contexts.