Background: According to the recent survey done by National Mental Health Survey (NMHS)-2016,it has found, in India every 10th person is suffering from some sort of depression or anxiety and in that 20% were either pregnant or lactating mothers. Research studies done earlier had clearly showed a significant association between maternal stress disorder and altered placental function and epigenetic changes. Aim: To assess the prevalence of psychological disorders among antenatal mothers and the factors influencing it. Methodology: A cross-sectional study was conducted for a period of 6 months in the department of obstetrics and gynaecology in a tertiary care hospital in Salem district. All antenatal mothers in the age group between 18 and 40 years reporting for regular antenatal check-up during the study period were included as our study subjects. A total of 240 study subjects had participated in the study. A semistructured and pretested questionnaire was made to collect the demographic details and the clinical history from the study subjects and along with it depression, anxiety and stress scale assessment tool which consist of 21 questions (DASS-21) with 7 items for each disorder was administered on all the study subjects to assess the presence of psychological disorders in antenatal mothers. Results: The prevalence of stress, anxiety and depression were 52.5%, 47.1% and 27.5% respectively. Most of them had mild stress disorder whereas mothers having anxiety type of psychological disorder majority of them were having moderate to severe type of anxiety disorder. All patients with depressionhad either stress or anxiety as a psychological comorbid condition. Primigravida mothers, mothers with previous history of abortion/still birth, people with history of infertility, history of psychological disorders in the previous pregnancy, history of medical and psychological disorders in the present pregnancy, family history of psychological disorders, history of domestic violence, history related to lack of family and social support and previous history of LSCS were found to be influencing factors for psychological disorders among antenatal mothers. Conclusion: Effective screening measures should be adopted to screen the antenatal mothers for all psychological disorders which would help to identify and manage it earlier and thereby preventing further complications both in mother and the new born.