In-order delivery of packets is a key issue in data communication networks. Re-sequencing delay and re-sequencing buffer size are two important measures in design, performance and optimization. In this paper, a large deviation result is proved for the re-sequencing buffer, which is fed bymparallelM/M/1 queues. The result provides a limit for the probability of a large buffer. This limit can be significantly simplified when themparallelM/M/1 queues are symmetric; that is, with the same arrival and service rates, respectively. The large deviation result obtained in this paper extends a recent result in the literature.