Upon its release, Young Foolish Happy was met with mixed reviews from music critics; while some reviewers found the album solid, others viewed it as formulaic and short of originality, and felt it lacks the "charm" of Lott's debut album, Turn It Up (2009). The album debuted at number eighteen on the UK Albums Chart with first-week sales of 18,503 copies, failing to match the commercial success of its predecessor. It spawned the UK number-one single "All About Tonight" and the top ten singles "What Do You Take Me For?" and "Kiss the Stars".
Lott began work on the album in Los Angeles in January 2011. In April 2011 she told Digital Spy that "[t]here are a couple of really cool collaborations on the album and I've already worked with some big people, but I can't say who they are just in case those tracks don't make the final cut", describing the sound as "still pop stuff, but maybe a little more soulful. That's the kind of thing that I'm into. That influence is stronger on this album." On 17 September 2011, Lott revealed the album title, which is inspired by The Tams' 1968 song "Be Young, Be Foolish, Be Happy". She stated, "It's a song I grew up listening to, from a young age. I grew up listening to a lot of soul music and I think this album sounds more this kind of way. It's a message that I've always really liked and I think it's important that need to people remember, it's just motivating and inspirational."
The album was initially scheduled for release in the United Kingdom on 7 November 2011, but it was eventually pushed back a week to 14 November. To celebrate the launch of the Pixie Collection, London-based women's clothing retailer Lipsy offered the first 10,000 customers a voucher to redeem on Lott's official website and obtain the album for £3 off.
Second single "What Do You Take Me For?", featuring rapper Pusha T, was released on 4 November 2011. The track reached number ten on the UK Singles Chart and number thirty on the Irish Singles Chart.
"Kiss the Stars" was released on 29 January 2012 as third single from the album, peaking at number eight in the UK and number thirty-three in Ireland.
Young Foolish Happy received mixed reviews from most music critics. Kim Dawson and John Earls of the Daily Star opined that "there's nothing foolish about [the] album" and that "[s]hirking teeny-bop options for proper soul passion helps her silky voice shine, especially on bump 'n' grind new single 'What Do You Take Me For?' featuring Pusha T."BBC Music's Fraser McAlpine felt that the album has "little of the magic that characterised her debut's highs" and criticised Lott for "working with songwriters who are capable of a finely tuned pastiche or two", but nevertheless cited "Nobody Does It Better" and "You Win" as "notable exceptions". The Evening Standard's Rick Pearson noted that Lott "opts for a more soulful direction this time around, something that works better with her wind tunnel of a vocal. She's still guilty of imitation rather than innovation, however, particularly on the synth-heavy 'All about Tonight', which is a craven rip-off of a Katy Perry record. But an identity is the only thing that's lacking here."AllMusic critic Stephen Thomas Erlewine named the "Motown-mythologizing" "Stevie on the Radio" one of the "brighter, better songs [on the album], largely because it has bigger beats and hooks", but commented that "the rest of the record has the form of a blockbuster record but lacks the requisite rhythms or hooks and its scale dampens Lott's spunky personality, which was her primary charm on her debut."
Ben Chalk of MSN Music wrote that while the ballads are "the real weak point", the uptempo material is "a vast improvement". Chalk continued, "Where debut Turn It Up showcased an original writing talent which belied the giggly blonde Essex girl persona, Young Foolish Happy sometimes lapses into a pastiche of Pixie's musical heroes." Duncan Gillespie of the NME found "All About Tonight" and "What Do You Take Me For?" to be "quite good", but dismissed Lott's "Jools Holland-ready retropop collaboration with Stevie Wonder" as "horrible, but still not horrible enough. Rather than righteous ire, you're left with only a sense of moral and cultural confusion, rather as if you'd caught yourself lusting after an ironing board." Simon Gage of the Daily Express stated that although Young Foolish Happy is a "pretty solid album of bouncy pop numbers", artists like Adele, Lady Gaga and Katy Perry leave "artists like Pixie out in the cold", adding that the album "has all the catchiness you would expect from last year's golden girl, but this year is a very different place."Virgin Media's Ian Gittins agreed, commenting that the album is "adequate, but never special: lacking Perry's raunch, Gaga's glitz, Adele's larynx or Jessie J's sass, it looks like Pixie Lott is set to remain a decidedly B-list pop star." Kevin Mathews of Singaporean newspaper Today expressed that the album "contains enough vocal and rhythmic hooks to keep the pop public sated as tracks like 'Come Get It Now', 'All About Tonight' and 'Nobody Does It Better' deliver in all these departments with some aplomb. The rest of Young Foolish Happy does not stray too far from this formula, which should keep Pixie Lott in demand for the immediate future."
Young Foolish Happy debuted at number eighteen on the UK Albums Chart, selling 18,503 copies in its first week. The following week, it dropped twenty-four places to number forty-two. The album was certified gold by the British Phonographic Industry (BPI) on 10 February 2012, having sold 70,843 copies by January 2012.Young Foolish Happy also entered the Irish Albums Chart at number thirty-three.