Test anxiety is the fear of students about negative results of the evaluative procedures. Low to moderate level of test anxiety is often thought beneficial for students. Test anxiety has two components worry and emotionality that are found in test anxiety research work. Academic Achievement encompasses students' academic potential. It is a common practice to promote students to next grades on the basis of their academic achievement scores. It aids in classifying students as pass or fail in examination. Present study was conducted to explore the effects of Test Anxiety on student's Academic Achievement at Secondary school level in Lahore. Causal Comparative research design was used to determine the causes of differences that were already therein the population. The population of study consisted of all secondary school students enrolled in district Lahore. A total of 840 students from 30 schools were selected as a sample from Lahore district. Test Anxiety Inventory Questionnaire was adapted and translated into Urdu in the study for data collection from secondary school students. The findings of the study indicate a negative relationship between test anxiety and academic achievement. Results showed that girls have higher test anxiety scores as compared to boys.