The Internet of Things (IoT) has become a significant force in the digital era that has revolutionized various industries, offering unprecedented levels of connectivity and automation. However, this rapid adoption has also made IoT ecosystems vulnerable to numerous security threats, including data breaches and complex cyberattacks. Traditional security measures, such as Intrusion Detection Systems (IDS), have been insufficient in protecting IoT networks due to their centralized structure and inability to adapt to the dynamic and resource-limited nature of IoT environments. To address these challenges, this research proposes a decentralized Collaborative Intrusion Detection System (CIDS) leveraging IPFS and blockchain technology. The architecture of the proposed CIDS is outlined, emphasizing its decentralized collaboration, trust management, and intrusion detection capabilities. Through a series of experiments, we evaluate the system’s performance in detecting common IoT attacks, managing latency, overhead, scalability, and trustworthiness. The results highlight the efficacy of the decentralized CIDS in fortifying IoT security and mitigating the unique challenges posed by IoT environments.