Among the emerging technologies for the fifth‐generation (5G) cellular networks, in‐band full‐duplex (FD) wireless communication and heterogeneous networks (HetNets) are two promising technologies, which can significantly improve the network capacity. Due to self‐interference (SI) and multiple sources of intercell interference, base station (BS)‐BS interference and user equipment (UE)‐UE interference in FD HetNets, interference management is a significant and challenging issue in such a network. To this end, in this article, we study the joint subchannel assignment and power control problem in the OFDMA FD HetNet. The joint subchannel assignment and power control problem in this network is formulated as an optimization problem to maximize the uplink and downlink sum throughput of the femtocell user equipments (FUEs) taking into account the maximum interference constraint imposed on the macrocell user equipments (MUEs) and the minimum throughput constraint of FUEs. Since the formulated problem is a nonconvex and intractable mixed integer nonlinear programming (MINLP) problem, we invoke variable change and linear approximation to reformulate and convert the problem into a tractable mixed‐integer linear programming (MILP) problem. Numerical results show that the optimal solution of the new MILP problem is very close to the optimal objective value of the original MINLP problem. The results also demonstrate that in an OFDMA FD HetNet, when all the UEs and the BSs are FD, approximately 50% improvement in the network throughputcan be achieved compared with a half‐duplex HetNet.