Ambient Assisted Living (AAL) system plays a vital role in the field of Internet of Things (IoT) based healthcare. AAL provides continuous monitoring of the patient and consequently increases the quality of the medical service. One of the major issues in AAL service is the security. In this paper, we have proposed an efficient Elliptic Curve Cryptography (ECC) based Ciphertext-Policy Attribute Based Encryption (CPABE) for the well accepted existing framework of AAL. The proposed CPABE is secured under Elliptic Curve Decisional Diffie-Hellman (ECDDH) assumption. We have evaluated the performance of the proposed CPABE with the existing schemes and result shows that the proposed scheme is more efficient in terms of computation overhead.