The increasing urbanization worldwide has imposed significant pressures on urban management systems, necessitating innovative solutions for sustainable development. The Internet of Things (IoT) has emerged as a transformative technology to optimize energy, water, and waste management systems in smart cities. This study employs a mixed-method approach to investigate the role of IoT in enhancing urban management in three leading cities: Singapore, Copenhagen, and Barcelona. These cities were selected due to their advanced adoption of IoT technologies and commitment to sustainability. Data were cleaned and analyzed using thematic and statistical methods, including regression modeling. The findings demonstrate that IoT significantly enhances urban sustainability by reducing inefficiencies, improving resource utilization, and promoting green initiatives. However, challenges such as high investment costs, data privacy concerns, and the digital divide persist. Recommendations include integrated policy frameworks, public-private partnerships, and community engagement to address these barriers and maximize IoT’s potential in urban management.