Copyright © 2014 by Lippincott Williams & Wilkins. Background: Despite concerns as to whether nurses can perform reliably and effectively when working longer shifts, a pattern of two 12-to 13-hour shifts per day is becoming common in many hospitals to reduce shift to shift handovers, staffing overlap, and hence costs. Objectives: To describe shift patterns of European nurses and investigate whether shift length and working beyond contracted hours (overtime) is associated with nurse-reported care quality, safety, and care left undone. Methods: Cross-sectional survey of 31,627 registered nurses in general medical/surgical units within 488 hospitals across 12 European countries. Results: A total of 50% of nurses worked shifts of r8 hours, but 15% worked Z12 hours. Typical shift length varied between countries and within some countries. Nurses working for Z12 hours were more likely to report poor or failing patient safety [odds ratio (OR) = 1.41; 95% confidence interval (CI), 1.13-1.76], poor/fair quality of care (OR=1.30; 95% CI, 1.10-1.53), and more care activities left undone (RR = 1.13; 95% CI, 1.09-1.16). Working overtime was also associated with reports of poor or failing patient safety (OR = 1.67; 95% CI, 1.51-1.86), poor/fair quality of care (OR=1.32; 95% CI, 1.23-1.42), and more care left undone (RR=1.29; 95% CI, 1.27-1.31). Conclusions: European registered nurses working shifts of Z12 hours and those working overtime report lower quality and safety and more care left undone. Policies to adopt a 12-hour nursing shift pattern should proceed with caution. Use of overtime working to mitigate staffing shortages or increase flexibility may also incur additional risk to quality.