Background and aims: Patients with ulcerative colitis have reduced health-related quality of life compared to the general population. Current treatment strategy aims to reduce patients’ symptoms and increase health-related quality of life. We investigated which symptoms of ulcerative colitis correlate to decreased health-related quality of life. Methods: Among 743 patients with moderate to severely active ulcerative colitis receiving biological therapy in a cross-sectional national study, we determined which disease-related symptoms, as measured by the Simple Clinical Colitis Activity Index, worsened health-related quality of life scores across the Short Health Scale dimensions, while adjusting for treatment, age, and clinical manifestation, and stratifying for sex, by means of multiple linear regression. Results: Patients with active disease had decreased health-related quality of life compared to those with inactive disease (median 5.8 (range 4.5–7.5) vs. 2 (0.8–3.3)). Both sexes had decreased health-related quality of life in all dimensions for the symptoms: bowel frequency during daytime (0.37–0.86 and 0.46–0.84), urgency of defecation (0.54–0.79 and 0.49–0.65) and blood in stool (0.50–0.75 and 0.36–0.54) for men and women respectively. Women were more often negatively affected by bowel frequency during night-time (4 domains vs. 1) and arthritis (5 domains vs. 3). In non-stratified analysis female sex is an independent predictor of lower health-related quality of life for 3 domains (0.38–0.53). Conclusions: Health-related quality of life was most prominently associated with bowel frequency during daytime, urgency of defecation, and blood in stool. Other symptoms associated for some health-related quality of life dimensions, and appear to vary between the sexes.