Mark Pytlik of Pitchfork gave the album a 7.4 out of 10, saying, "what's interesting about Happy Birthday! isn't just that it fuses together the most unfashionable or discarded elements of electronic music's recent history, but that it manages to sound so fresh in doing so." A review for Tiny Mix Tapes awarded the album 3.5 out of 5, praising Modeselektor's eclectic approach while emphasizing the duo's ability to fuse disparate influences into a coherent album flow.