Wireless Sensor Networks are installed in hostile areas. The security issues in wireless sensor networks are very important. Getting secure links between nodes is a challenging problem in WSNs. They are more vulnerable to security attacks than wired networks. In order to protect the sensitive data in WSN can be protected using secret keys to encrypt the exchanged messages between communicating nodes. Key management is essential for many security services such as confidentiality and authentication. The symmetric or asymmetric key cryptography or Trusted-server schemes are used to solve this problem. Asymmetric key cryptography increases network security but it increases computational, memory, and energy overhead. Symmetric key cryptography provides less security and it is efficient key management scheme. Trusted server schemes use key management server. Because there is usually no trusted infrastructure it is not very suitable for sensor networks. In this paper, we have proposed Mobile Agent (MA) Based Key Distribution (MAKD). In MAKD, Mobile Agents are used for dissemination of public keys and update of shared keys. Each sensor node constructs different symmetric keys with its neighbors, and communication security is achieved by data encryption and mutual authentication with these keys. Simulation results show that MAKD is scalable and with less memory overhead.