Aim: To categorize the causes of AUB in age group 35 -55 years women in context to PALM-COEIN classification system and its clinicopathological correlation. Materials and method: This prospective observational study was carried out in the Gynecological OPD (Out Patient Department) at Hind Institute of Medical Sciences, Mau, Ataria, Sitapur, Uttar Pradesh. After fulfilling the inclusion and exclusion criteria, 150 women of age group (35 – 55 years) with any type of menstrual complaints attending Gynecological OPD and IPD were included in the study.The structured history of menstrual pattern, contraceptive history and other details, followed by general physical, systemic and thorough gynecological examination in context touterus, cervix and adnexa was assessed. Endometrial samples were collected through procedures like by endometrial biopsies, then analyzed histopathologically. Causes of AUB were classified using the PALM-COEIN system, which includes categories like polyps, adenomyosis, leiomyoma, malignancy, coagulation disorders, ovulatory disorders, endometrial disorders, iatrogenic causes, and those not yet classified. Relevant investigations included Complete Blood Count, Coagulation profile, Iron profile, Thyroid Function Test, and Blood Sugar levels. These results were correlated with clinical and histopathological findings to establish a comprehensive understanding of AUB causes in the study population. Results: The study included 150 women 35-55 with AUB, classified using the PALM-COEIN system. Key findings revealed a diverse range of AUB causes: polyps (12.67%), adenomyosis (18%), leiomyomas (26%), ovulatory.dysfunction (23%), endometrial issues (9.33%), iatrogenic causes (4.67%), and unclassified cases (1.33%). There was a high prevalence of comorbidities, including obesity (42%), thyroid disorders (37.5%), hypertension (24%), and diabetes (27%). Frequent and heavy menstrual bleeding were common symptoms across various AUB subtypes. Conclusion: Our study contributed to the growing body of literature on AUB, providing insights into its multifaceted nature, diagnostic challenges and tailored therapeutic strategies. Further research is required to refine diagnostic algorithms and treatment protocols.