Healthcare industry is digitising its healthcare operations and generating huge amounts of sensitive medical data to make prompt and informed decisions in patients’ health diagnosis and care. The healthcare industry is subjected to a variety of security threats (e.g., data tampering, theft, and counterfeit drugs). Blockchain is gaining traction to address such security threats and improve data integrity by turning healthcare operations into decentralised, transparent, and immutable manners. However, there is conceptual ambiguity and semantic gaps about blockchain as a countermeasure solution for healthcare security threats. In this work, we use the web ontology language to create blockchain-based security ontology (HealthOnt) to remove conceptual ambiguity and semantic gaps. The HealthOnt offers coherent and formal information models that present blockchain as a countermeasure solution for security threats of traditional healthcare applications.