Patient recruitment for clinical trials is known to be a challenging aspect of clinical research. There are multiple competing concerns from the sponsor, patient and principal investigator's perspectives resulting in most clinical trials not meeting recruitment requirements on time. Conducting under-enrolled clinical trials affects the power of conclusive results or causes premature trial termination. The Blockchain is a distributed ledger technology originally applied in the financial sector. Its features as a peer-to-peer system with publicly audited transactions, data security, and patient privacy are a good fit for the needs of clinical trials recruitment. The "Smart Contract" is a programmable self-executing protocol that regulates the blockchain transactions. Given current recruitment challenges, we have proposed a blockchain model containing multiple trial-based contracts for trial management and patient engagement and a master smart contract for automated subject matching, patient recruitment, and trial-based contracts management.