During salary negotiation should I mention a competing offer?

During a salary negotiation, whether or not you mention a competing offer is up to you. If you believe that the companies will bid for your services, it could result in a higher salary for you overall. You have to use your own judgment and decide how badly the two companies want you. Some people do not feel comfortable using this tactic. If you think that the employer would be insulted, do not use the tactic. Salary negotiation is an inexact science and what works in one negotiation may not work in another.