The present study aimed at examining the relationship between foreign language anxiety and academic achievement of Pakistani undergraduate students to show how it affected their performance. The study also investigated students’ Foreign Language Anxiety level variations according to their gender and discipline of study. Data were collected from 232 undergraduate participants majoring in English, Psychology, Economics, BBA, Urdu, Zoology, Botany, and Chemistry from a major public college of Sialkot, by using a mixed method approach: quantitatively through questionnaire and qualitatively through semi-structured interviews. Mean scores, t-test, Pearson Correlation and one-way ANOVA were employed to analyze the data. The results revealed that participants in this study had high level of reading and writing anxiety and moderate level of speaking anxiety raised mostly by the fear of incorrect pronunciation, speaking without preparation, fear of reading English aloud, and unfamiliarity with English culture and ideas. Conversely, negative correlation between students’ level of anxiety and their academic achievement was prevalent in the data. In terms of gender, male students were found to be more anxious than female students. Besides, a significant difference between English major and English non-major students was noted as English non-major students had high level of anxiety. Apart from that, the interview results elucidated on the role of the teachers in the success or failure of language learning process. Finally, the study suggests that the classroom atmosphere should be stress free and learner friendly to successfully achieve second language learning.