Ulcerative colitis (UC) is a chronic idiopathic disease characterized by an inflammatory response largely limited to the colonic mucosa. Being a lifelong condition, ulcerative colitis has a significant psychological and social impact on patients. Vitamin D can restore the gut mucosal barrier in addition to regulating immunological responses. Vitamin D may improve a patient's quality of life and reduce the symptoms of ulcerative colitis by having an anti-inflammatory impact on the intestines and being instrumental in mucosal repair. We randomized newly diagnosed patients of ulcerative colitis either to receive standard therapy or oral 4000 IU vitamin D3 in addition to standard therapy for 12 weeks in this prospective, parallel-group, randomised, comparative clinical research. Group I showed reduction from 7.20 ± 0.29 at baseline and 6.17± 0.29 at 12 weeks in Mayo score with standard therapy at week 12 in comparison with Vitamin D adjuvant standard therapy which showed reduction from 6.67 ± 0.37 at baseline and 5.37 ± 0.32 at 12 weeks in Mayo score, indicating Vitamin D adjuvant therapy to be better in reducing disease activity. Quality of life was evaluated using the Short Inflammatory Bowel Disease Quality of Life Questionnaire (SIBD-QOL) at weeks 0, 4, 8, and 12. After completion of therapy at 12 weeks Group I SIBDQOL score increased to 44.50 ± 2.01 and Group II increased to 51.27 ± 2.13), with the difference being statistically significant.