Introduction: There is a number of pathological, epidemiological, molecular basis which could establish an association between the liver dysfunction and thyrotoxicosis. Thyrotoxicosis is defined as the state of thyroid hormone excess while Hyperthyroidism is the result of excessive thyroid function. Aims: Assessment of liver function in the background of newly diagnosed thyrotoxicosis, comparison between liver function and different types of thyrotoxicosis and co-relation of clinical activity score (CAS) and liver function test (LFT) in Graves” disease. Materials and Methods: The present study was a Institution based Cross-sectional study. This Study was conducted from 18 months (From 1st January, 2020 to 30th June, 2021) at Department of General Medicine, endocrinology outdoor of Calcutta National Medical College and Hospital, Kolkata. Result: Chi-square ( 2 ) test showed that there was significant association between level of total bilirubin and types of thyrotoxicosis of the patients (p=0.0059).High level of total bilirubin was prevalent in significantly higher proportion among the patients with Multinodular Goitre (100.0%) as compared to other types of thyrotoxicosis (p<0.01) Conclusion: In conclusion, the results of our study suggest that thyrotoxicosis is associated with abnormal liver biochemical tests in about two-third of the presenting cases and the most commonly elevated parameters are ALT and AST followed by ALP levels. Therefore, patients presenting with unexplained hepatic abnormalities require evaluation of the thyroid function.