Although not released until 1986, Boston recorded "Can'tcha Say (You Believe in Me)" over 1981, 1982 and 1983. According to the Third Stage liner notes, the song is about a reunion. Scholz used the Rockmanamplifier he invented to produce an effect in which the electric guitars sound like violins. "Can'tcha Say (You Believe in Me)" was the first song on which Scholz recorded his guitar part using a Rockman, in conjunction with a ten band equalizer for changing sounds.
Boston Phoenix critic Milo Miles criticizes "Can'tcha Say (You Believe in Me)" as "tedium." He singles out the line "Where there's a will there's a way" as an example of the song's "prosaic, cliched lyrics." However, Billboard Magazine regarded the song as one of the "best bets" to follow up on the success of the #1 single from Third Stage, "Amanda."Los Angeles Times critic Steve Pond praises the "persuasive" sound at the climax, which he likens to the sound of "a couple dozen guitars" revving up. Jerry Spangler of the Deseret News praised the song as a ballad that sounds like a "sure-fire winner". Philip Booth of the Lakeland Ledger praises the song's "a capella vocal opening." Tom Alesia of The Wisconsin State Journal regards the song's title as Boston's worst.