In the era of the Internet of Things (IoT), it is a promising way to improve system energy utility and better meet users’ requirements for Quality of Service (QoS) via integrating nonorthogonal multiple access (NOMA) and mobile-edge computing (MEC) technologies. In light of this idea, we investigate device access, subchannel division, and transmission power allocation for NOMA-enabled IoT systems. To maximize the energy utility of IoT systems while satisfying the minimum demands of IoT Devices (IoTDs) on achievable uplink data rate, a joint optimization problem is formulated with the consideration of device access, subchannel division, and transmission power allocation. Due to the nonconvexity of this problem, we propose an alternating optimization algorithm aiming to find the optimal solution. The proposed algorithm first decomposes the joint optimization problem into three subproblems through the block coordinate descent (BCD), and then obtains the near-optimal solution by solving the decomposed subproblems alternately. Extensive simulations validate our analysis for the convergence of the proposed algorithm. The numerical results demonstrate that the proposed algorithm significantly outperforms the benchmark algorithms in terms of improving system energy utility.