Ratworld received generally favorable reviews from critics. On Metacritic, it has been given a score of 68 out of 100 based on 13 reviews.[1] Stephen Ackroyd of DIY raved the album, saying "Ratworld is that rarest of beasts—a debut album that’s got a backstory running deeper than all six seasons of Lost, but still sounds like it’s delivered without any requirement for effort whatsoever." Ackroyd gave the album five out of five stars.[5] Al Horner at NME gave the album 8/10 praising their sound and musicianship, saying that Ratland "may relish a world on the brink of chaos, but this is a band with their shit together."[10] Pitchfork Media's Evan Rytlewski gave the album 7.1/10 complimenting the band's embracing of their influences, as well as their energy. Rytlewski wrote Menace Beach "bottles and concentrates the exuberance of [1990s] era's alterna-pop".[11]
Andy Peterson of Contactmusic.com gave the album a more mixed-review. Peterson felt that the album "their resolutely DIY aesthetic in the wrong hands could be a minefield of derivation"; however, he backpedaled and said the despite this that Ratworld " manages to bottle enough psy-kookiness in the thirteen tracks here to hold even the most wayward of attentions".[4]