The search for factors and determinants of effective foreign (second) language acquisition (FLA/SLA) is an interdisciplinary problem that is becoming more and more practically important in the modern globalising world. The purpose of this study is to examine and compare the correlation between personality traits and the foreign language proficiency (FLP) level among students of various university specialties. The total sample includes 241 first- and second-year undergraduate students (74% females), of which 128 students (82.5% females) study at the Linguistics Department and 113 students (64% females) belong to other departments. All the students learn English as a primary foreign language (FL). The Five-Factor Model (FFM) of personality traits (Neuroticism, Extraversion, Openness, Conscientiousness, and Agreeableness) were measured by the NEO Five-Factor Inventory (Russian adaptation by S. Biryukov and M. Bodunov). In testing the foreign language proficiency levels, we used the traditional Academic Performance Index (semester Final Grades in English) and assessments of the foreign language proficiency levels made by English teachers in relation to their students according to the Foreign Language Proficiency Scale (10 indices and the total score) developed by the authors. To process the data in the R software environment, version 3.5.2, the methods of descriptive statistics, Cronbachs alpha and Macdonalds omega coefficients, Spearmans rank correlation analysis and Wilcoxons T -test were used. The findings of our research showed that FLP is most closely related to Openness in linguistics students and to Conscientiousness in non-linguistics students. These facts should be taken into account by the developers of programmes for psychological and pedagogical support of the FL learning process in Russian universities.