The social nature of mobile agent and its ability to carry its principal’s confidential information necessitate the need to secure its communication with other agent(s) in an agent system. Most importantly, an agent communication security mechanism must be able to prevent unknown or visiting agent from participating in legitimate agent communication. Most of such mechanisms adopt two-pass authentication technique without due consideration of the enormous overheads generated by the mechanisms. These overheads are more noticeable in multi-agent system based applications with large number of agents such as smart grid. The main focus of this paper therefore, is to design a lightweight mechanism for agent communication confidentiality protection in a local area network (LAN) or intranet using one-pass authentication approach. The proposed mechanism adopted both symmetric and asymmetric cryptosystems to protect agent certificate transmission between task agents and agent execution host. The results show that the memory utilization, communication and computation costs of the proposed mechanism are remarkably lower than that of the two-pass authentication based mechanisms.