Contemporary music critics spoke favourably of The Family Jewels, and welcomed its diverse production. The record debuted at number five on the UK Albums Chart with first-week sales of 27,618 copies, and remains Diamandis' highest-selling debut week of her career. The project was eventually certified gold by the British Phonographic Industry and has sold 177,268 units in the United Kingdom. The Family Jewels performed moderately on international record charts; it peaked at number 138 on the US Billboard 200, and became Diamandis' first charting project in the United States.
The Family Jewels was supported by five singles, all of which were supplemented by accompanying music videos. "Mowgli's Road" was released as the lead single from the record on 13 November 2009, although "Hollywood" became its first charting track after reaching number 12 on the UK Singles Chart. Follow-up singles "I Am Not a Robot", "Oh No", and "Shampain" respectively peaked at numbers 26, 38, and 141 in the United Kingdom. The record was additionally promoted by Diamandis' headlining The Family Jewels Tour, which visited Australia, Europe and North America from January 2010 through December 2011.
Diamandis explained that the album is "a body of work largely inspired by the seduction of commercialism, modern social values, family and female sexuality". She also describes it as "a really diverse album stylistically speaking because I'm such a flexible writer, so there's a lot of pop on it, but there's kind of a lot of leftfield experimental stuff as well. It's basically an album about what not to be."
"Mowgli's Road" was released as the album's lead single on 13 November 2009. "Hollywood" was released as the album's second single and Diamandis's first major release on 1 February 2010. It reached number twelve on the UK Singles Chart. "I Am Not a Robot" was released as the album's third single on 26 April 2010. The song reached number twenty-six on the UK Singles Chart. "Oh No!" was released as the album's fourth single on 2 August 2010 only in the UK and Ireland. It peaked at number thirty-eight on the UK Singles Chart. "Shampain" was released as the album's fifth and final single on 11 October 2010 only in the UK and Ireland. It reached number 141 on the UK Singles Chart.
The Family Jewels received mostly positive reviews. At Metacritic, which assigns a normalised rating out of 100 to reviews from mainstream critics, the album received an average score of 68, based on 21 reviews, which indicates "generally favorable reviews". Hugh Montgomery of Q magazine noted that the album presented a range of different styles, skipping "from glam-disco ('Shampain') and bubblegum punk ('Girls') to quavering piano laments ('Obsessions') and cabaret ditties ('Hermit The Frog')", adding that the singer's "imaginative reach" was "complemented by a winning pop savviness." However, The Independent 's Andy Gill gave the album a negative review saying it "demonstrates the inevitable workings of entropy on pop methodology" and describes "Shampain" and "Hermit the Frog" as "every bit as annoying as their punning titles, with queasy, prancing piano and synth figures labouring away methodically, Mika-fashion, while she searches unsuccessfully for worthwhile lyrical routes".
Luke O'Neil from The Phoenix stated that "[t]he likes of Kate Nash and company have flitted through this piano siren/exuberant dance-diva territory, but never mind, because this gorgeous genre starts now." Lou Thomas from BBC Music commented that "[t]he consistently diverting changes in style across the album are fine—the wonky 80s shoulder-pad pop of 'The Outsider' is nothing like anything else here, for example. But over 13 songs of Sparks-voice and many similar staccato piano riffs listeners may feel bludgeoned by Marina and her slightly overbearing presence." Leonie Cooper from NME rated the album nine out of ten stars and wrote, "An album with a distinct dual personality, Marina's dazzling The Family Jewels pitches the confident, MTV Awards-headlining superstar of our dreams against a more self-deprecating girl-next-door Marina who's dead set on Supertramping and vamping her way out of her fug."
The NME placed the album at number thirty-three on its list of the Top 75 Albums of 2010.
The Family Jewels debuted at number five on the UK Albums Chart with first-week sales of 27,618 copies. It remains Diamandis' best-selling debut week, after her second studio album Electra Heart entered the chart at number one with first-week sales of 21,358 units.The Family Jewels was later certified gold by the British Phonographic Industry, and had sold 177,268 copies in the United Kingdom as of May 2012. The record debuted at number seven in Greece and number nine in Ireland; it was eventually certified gold by the Irish Recorded Music Association.