Background: Job satisfaction is a fundamental factor affecting nurse well-being, retention, and healthcare system performance. Aim: This study explores the determinants of job satisfaction among nurses, with particular emphasis on the differences between temporary agency nurses and those in permanent positions in North Rhine-Westphalia, Germany. Methodology: A cross-sectional study was conducted to assess job satisfaction among nurses working under both temporary agency and permanent employment contracts. Data were collected from a sample of 195 nurses using the Job Satisfaction Survey (JSS), a standardized instrument designed to measure multiple domains of job satisfaction. The survey included items related to supervision, salary, promotion opportunities, work relationships, and benefits. Statistical analyses were performed to identify and compare job satisfaction levels between the two employment groups. Results: Temporary nurses reported consistently higher satisfaction than permanent nurses across most domains of the Job Satisfaction Survey. Supervision was the most positively rated factor (97.9% of temporary vs. 72.2% of permanent nurses), while pay (73.0% vs. 11.1%) and benefits (51.8% vs. 9.3%) also showed large disparities. Promotion opportunities were rated lowest by both groups (7.1% vs. 3.7%), and satisfaction with co-worker relationships remained stable across groups (63.1% vs. 63.0%). The most pronounced contrast was observed in overall job satisfaction: 61.7% of temporary nurses reported being satisfied compared with only 5.6% of permanent nurses. Regression analysis confirmed that permanent employment was negatively associated with satisfaction, whereas higher educational attainment predicted higher satisfaction with pay and overall job satisfaction. Conclusion: The findings reveal significant and counterintuitive differences in job satisfaction between temporary and permanent nurses. Contrary to expectations, temporary nurses consistently reported higher satisfaction across most domains of work life. Addressing issues related to compensation, career progression, and job stability is essential to enhance satisfaction and reduce turnover. Healthcare organizations should implement targeted strategies that acknowledge the distinct needs of both employment groups and foster a supportive working environment.