The Brown-crested Flycatcher is most similar to the other flycatchers in the genus Myiarchus: Great Crested, Ash-throated and Dusky-capped. Ash-throated and Dusky-capped are smaller with smaller, slimmer bills. Great Crested has a darker gray throat and breast while Ash-throated has paler yellow underparts. Ash-throated and Great Crested have rustier tails. The calls of these very similar species are an excellent way to distinguish them. Some species of kingbirds are similar but have paler heads and lack rusty in the tail.
Length and wingspan from: Robbins, C.S., Bruun, B., Zim, H.S., (1966). Birds of North America. New York: Western Publishing Company, Inc.