The rapid growth of small Internet connected devices, known as the Internet of Things (IoT), puts resilient challenges to create secure, private infrastructures. Each IoT device with unique identifier is able to communicate with other devices by enabling their self-identification to other devices. Hence, the security of the device, network and data becoming a big concern. Authentication and access control are two key techniques to prevent a computer or network component from being compromised. To enhance the security of IoT devices various authentication and access control schemes including authorization methods are proposed. Traditionally, authentication method such as Kerberos authentication protocol, etc. are used for network authentication. However, these protocols are not fits for constrained devices in IoT environment. Moreover, devices in constrained environments need more interoperable authentication and access control mechanisms to ensure the security of IoT devices. In this paper we proposed a security enhanced integrated approach of mutual authentication mechanism using Elliptical Curve Cryptography (ECC) and also a capability based access control mechanism to protect the IoT devices from unauthorized users. Our wok provides the end-to-end security and meets up the requirements of constrained devices. We have analyzed the proposed work against various attacks and shown the performance evaluation in comparison with related works.