The Internet of Things (IoT) technology along with cloud computing has gained much attention in recent years for its potential to upgrade conventional healthcare systems. Outsourcing healthcare data to a cloud environment from IoT devices is very essential as IoT devices are lightweight. To maintain confidentiality and to achieve fine‐grained access control, the ciphertext policy attribute‐based encryption (CP‐ABE) technique is utilized very often in an IoT‐based healthcare system for encrypting patients' healthcare data. However, an attribute revocation may affect the other users with the same attribute set, as well as the entire system due to its security concerns. This paper proposes a novel CP‐ABE‐based fine‐grained access control scheme to solve the attribute revocation problem. The proposed technique includes multiple attribute authorities to reduce the work overhead of having a single authority in the traditional CP‐ABE systems. In addition, the proposed scheme outsources the decryption process to a decryption assistant entity to reduce the decryption overhead of the end‐users. To prove the efficiency of the proposed scheme, both formal security analysis and performance comparisons are presented in this paper. Results and discussion prove the effectiveness of the proposed scheme over some well‐known schemes.