There has been a rise in cyberattacks in contemporary society, executed by both skilled and unaware individuals. Such attacks occur across various domains. Beyond the medical sector, this domain is considered one of the most critical sectors necessitating a heightened focus on cyberattacks, owing to the imperative for Electronic Medical Records (EMR) security within healthcare administration systems. It is essential to disseminate each record contained within an electronic medical record (EMR) to various healthcare providers. This complicates access and increases the probability of attacks against data integrity, such as Sybil attacks, data tampering, and injection attacks. Health records management—such as data breaches, interoperability, and limited patients’ ownership over data—has its issues, which can be addressed by using blockchain as a new-generation secure, decentralized, and open data management technology for healthcare. Furthermore, healthcare providers prioritize interoperability while accessing electronic medical records (EMRs). This study presents a novel solution called Medichain to secure patient medical records with Blockchain technology. Consequently, each Blockchain block contains a compilation of patient records. The user may incorporate the list of items into the block as a JSON file; once added, the data becomes immutable. The proposed method involves hashing the records in the block using cryptographic algorithms, followed by proof of work and Merkle tree creation. We have developed a web-based application enabling hospital personnel to input and retrieve patient records. We executed a comprehensive simulation of the entire methodology with Python. As a result, we have effectively improved the security of electronic medical records (EMR) against data tampering and injection attacks, as well as ensuring interoperability through the suitable development of a web-based application.