Homorazzi.com reporter Donovan Pagtakhan named it the group's best song to date and a "catchy pop track with a folk vibe", while Maximum Pop! said the track "feels like a tune you'd pump in your car when riding with your girlfriends. Brad Stern from MTV labeled it a "certifiable, Dr. Luke-produced smash" packed with "chant-along-friendly hooks". Jason Lipshutz from Billboard quipped "the group uncovers the winning pop formula that previous single "Vacation" failed to unlock." Melissa Redman from Renowned for Sound gave "Ugly Heart" three and a half stars out of five. She called the tune "cliche", but thought it had a "catchy appeal" and was a "nice effort from G.R.L" overall. Sugarscape.com's Carl Smith dubbed it an "insanely sassy single". Igee Okafor writing for magazine The Source likened "Ugly Heart" to "up-tempo and high-energy" releases by Ke$ha. They described the ukulele as "infectious" and the vocals as "powerful and impeccable". Billboard named the song #50 on their list of 100 Greatest Girl Group Songs of All Time.
