The film was quite popular in its day. Here is a round up of reviews and articles drawn from the Louise Brooks Society archive.
Soanes, Wood. "Curtain Calls." Oakland Tribune, December 31, 1936.
--- "Louise Brooks is certainly starting her come-back from the lowest rung of the ladder. She is one of a hundred dancers in the ballet chorus of Grace Moore's When You're in Love emerging from Columbia. In 1929 she was featured in The Canary Murder Case."
anonymous. "Moore's You're in Love Swell; Star at Her Best." Hollywood Reporter, February 13, 1937.
--- "With a more substantial story than the last two Grace Moore vehicles, When You’re in Love is a signal triumph for the foremost diva of the screen, for Cary Grant who should soar to stardom as result of his performance in this, and for Robert Riskin, here notably handling his first directorial assignment."
Maloney, Russell. New York World-Telegram, February 19, 1937.
--- "A glib and amusing discussion of things romantic and musical, it is one of the best films Miss Moore has had - a literate, tonic, diverting entertainment that may be attended by all in search of witty comedy and lilting melody."
Cinemaid. "Grace Moore Humor, Songs Enliven New Musical." San Francisco Call-Bulletin, February 26, 1937.
--- "Robert Riskin has equipped Miss Moore and Mr. Grant with a very amusing screen play and he has directed it to make the most of the humorous aspects of a marriage of convenience."
anonymous. "Torch-Song Diva." Literary Digest, February 27, 1937.
--- "Riskin, recalling shrewdly that scenarios were at their level best when minor characters were shuffled around in such a way as to sharpen the importance of majors in the cast, brings the same formula into his direction, and with like triumphant results for the cinema."
Schallert, Edwin. "Grace Moore Film Clever Offering." Los Angeles Times, March 4, 1937.
--- "However, the qualities of the film are quite Riskinish. There's no mistaking that."
Harris, Mary. "A Grace Moore Hit is on View at the Earle." Washington Post, March 6, 1937.
--- "Grace Moore gallantly sets out to prove she can suit every musical taste in her latest picture."
Wagner, Rob. Rob Wagner's Script, March 6, 1937.
--- "Here is the perfect combination - the director who writes his own script and delivers perfectly. . . Yes, I’m raving, not only because I’m 'a little boy who likes motion pictures,' as Fulton Oursler says, but because I’m a priest of beauty; and this picture thrilled me."