The deployment of 5G networks has significantly improved connectivity, providing remarkable speed and capacity. These networks rely on Software-Defined Networking (SDN) to enhance control and flexibility. However, this advancement poses critical challenges including expanded attack surface due to network virtualization and the risk of unauthorized access to critical infrastructure. Since traditional cybersecurity methods are inadequate in addressing the dynamic nature of modern cyber attacks, employing artificial intelligence (AI), and deep reinforcement learning (DRL) in particular, was investigated to enhance 5G networks security. This interest arises from the ability of these techniques to dynamically respond and adapt their defense strategies according to encountered situations and real-time threats. Our proposed mitigation system uses a DRL framework, enabling an intelligent agent to dynamically adjust its defense strategies against a range of DDoS attacks, exploiting ICMP, TCP SYN, and UDP, within an SDN environment designed to mirror real-life user behaviors. This approach aims to maintain the network’s performance while concurrently mitigating the impact of the real-time attacks, by providing adaptive and automated countermeasures according to the network’s situation.