Mmhmm received generally positive reviews from music critics. John D. Luerssen of
AllMusic stated, "After moving away from their patented pop/punk approach on 2003's ''Two Lefts Don't Make a Right...But Three Do
, spiritual rockers Relient K revert back to their proven formula of yore on MMHMM'' [...] At times the lads in Relient K come off a bit too mainstream for their own good, but you've got to give them thanks for not going straight for the jugular the way so many other Christian rockers might." Steve Best of
Cross Rhythms remarked, "the power pop punks have upped the ante with a mixture of tongue-in-cheek fun ('My Girl's ex-Boyfriend') and reflection ('Who I Am Hates Who I've Been') which never dips in quality and credibility. Helmed by the ridiculously talented and tasteful Mark Lee Townsend, this set will have the likes of
Busted and
McFly crying into their Sunny D's."
IGN wrote that the album "manages to be spiritual without being heavy-handed, varied without sounding spastic, and clean-sounding without coming off as manufactured." Josh Taylor of Jesus Freak Hideout described the album as their "most aggressive work to date." He noted, "There is growth, but it's in much more subtle ways than on past releases. This can most likely be attributed to the fact that Relient K had almost perfected their art with
Two Lefts..., and
Mmhmm simply builds on what was already a very good thing, while tactfully experimenting with different sounds." Kenneth Yu of
PopMatters said the album "has successfully evoked those memories of angst ridden teen-hood past, my search for identity and the coming to terms with my faith facilitated by bands-of-yore." Writing for
Stylus Magazine, Justin Cober-Lake gave the album a mixed review, stating, "Right now, the band isn't taking the chances or reaching far to enough to stay interesting for an album-length effort, but they do have their moments. Their lyrics are their strength; they've been able to bring out the seriousness of their concerns without losing the joy or goofiness. If the music catches up, they'll be a reliable act." Brian Shultz of
PunkNews also gave a mixed review for the album, "For the band themselves it seems like a landmark effort. They've managed to slowly mature over the years, lyrically anyway, but it especially shows this time around. The sugary choruses here sound pretty similar, and it's nothing new by a longshot, but
Mmhmm is a moderately enjoyable effort, as opposed to how irritating some of their contemporaries can be." ==Commercial performance==