PURPOSE: To analyze the incidence, risk factors, and outcomes of cataract surgery complicated by a dropped nucleus. SETTING: Patients who have received cataract surgery in 18 European countries. DESIGN: Retrospective cross-sectional register-based study. METHODS: Data from the European Registry of Quality Outcomes for Cataract and Refractive Surgery (EUREQUO) were analyzed. The EUREQUO contains preoperative baseline, intraoperative, and follow-up data. Intraoperative data include dropped nucleus as a complication. Baseline data such as demographic data, ocular comorbidities, surgical difficulties, and visual and refractive outcomes were tested for association with a dropped nucleus for the study period from January 1, 2008, to December 31, 2018. RESULTS: The number of reported patients with complete data was 1 715 348. Dropped nucleus was reported in 1221 eyes (0.071%) during the study period. White cataract, previous vitrectomy, poor preoperative visual acuity, small pupil, pseudoexfoliation, diabetic retinopathy, and male sex were significantly related to dropped nucleus. Year of surgery showed a significant trend of decreasing occurrence of dropped nucleus over time. Eyes with the complication of a dropped nucleus also had a poorer visual and refractive outcome compared with eyes with existing risk factors but no such complication. CONCLUSIONS: Many risk factors for dropped nucleus complications were identified. A significant trend of decreasing occurrence of dropped nucleus was found for the study period. The visual and refractive outcome was poorer for eyes with a dropped nucleus.