Today's internet of medical things (IoMT) devices has revolutionized healthcare by enabling the development of assistive systems that enhance patient care and improve healthcare outcomes. However, the increasing connectivity and data exchange in IoMT systems raise issues about cybersecurity and patient data privacy. This chapter explains the application of blockchain-based cybersecurity in IoMT-based assistive systems. Blockchain technology offers a decentralized and immutable ledger that ensures the integrity, security, and transparency of data in IoMT systems. By adding blockchain, cybersecurity challenges in IoMT can be addressed effectively (with providing several benefits, including enhanced data protection, secure identity management, and robust access control mechanisms). Generally, in a blockchain-based cybersecurity framework for IoMT, patient health data is stored in encrypted form on the blockchain, preventing unauthorized access/ tampering. Smart contracts, programmable blockchain protocols, can automate access control and consent management, etc.