Summary: We study customers’ strategic behavior and social optimization in vacation queues with \(N\)-policy under two partial-information scenarios. In scenario 1, only the server’s status is observable. We find that avoid-the-crowd/follow-the-crowd behavior exists when the server is busy/idle. In scenario 2, only the queue length is observable. The customers’ equilibrium threshold strategy is the same as that in a fully observable system; whereas, the optimal control policy in a fully observable case is sometimes, but not always, implementable in scenario 2.