Background: Upadacitinib (UPA) is a new oral selective Janus Kinase (JAK) inhibitor that has shown high efficacy in the treatment of ulcerative colitis (UC). We present data from a multicenter real-world study. Methods: To assess efficacy of UPA, Total Mayo Score (TMS), fecal calprotectin (FC), endoscopy, and intestinal ultrasonography (IUS) were performed. Results: The study population included 76 patients. An amount of 26.3% of the patients were biologics and small molecules-naive, while 73.7% were exposed. By Week 8, 93.4% of the patients had achieved a clinical response (94.7% naive vs. 92.9% exposed), 72.4% achieved endoscopic improvement (78.9% vs. 71.4%), and 57.9% had clinical remission (78.9% vs. 51.8%). Endoscopic remission was achieved in 31.6% of patients (35.0% vs. 30.4%) and biochemical remission in 82.1% (53.3% vs. 68.3%). All of the results were not significantly different apart from the steroid-free clinical remission—36.8% (68% vs. 26.8%, p = 0.002) after 8 weeks of follow-up. IUS was performed in 33 patients. Bowel wall thickness (BWT), inflammatory fat (iFAT), color Doppler signal (CDS), loss of bowel wall stratification (BWS), and Milano Ultrasound Criteria (MUC) had decreased significantly by Weeks 4 and 8 (p < 0.005 for all). Correlation between the IUS results and TMS, FC and endoscopic remission in Week 8 was confirmed (p < 0.001). UPA was well tolerated, and no new safety signals were registered in our group. Conclusions: In this study, UPA was confirmed to be safe and highly effective in inducing remission in UC patients in both the naive group and the biologically exposed patients. The correlation between the IUS results and TMS, FC, and endoscopic remission provides valuable information for clinicians.