The album peaked at number 10 on the UK Albums Chart, and was ranked number 991 in the 2000 book All Time Top 1000 Albums.
This was the only Depeche Mode album with Vince Clarke as a member. Clarke wrote most of the songs for the band, before departing to form Yazoo and later Erasure.
The album is significantly lighter in tone and melody than their later work, a direction which can largely be attributed to Clarke's writing. After he left, Martin Gore took over songwriting duties, writing almost all of the band's material. Later albums written by him would explore darker subjects and melodies.
When interviewed by Simon Amstell for Channel 4's Popworld programme in 2005, Gore and Fletcher both stated that the track "What's Your Name?" was their least favourite Depeche Mode song of all time.
Upon its release, Speak & Spell received generally positive reception from critics. Record Mirror praised Depeche Mode's smart simplicity and noted the album offers "much to admire and little to disappoint." Reviewer Sunie commented that the band's chief skill "lies in making their art sound artless; simple synthesiser melodies, Gahan's tuneful but undramatic singing and a matter-of-fact, gimmick-free production all help achieve this unforced effect." As a whole she describes it as "a charming, cheeky collection of compulsive dance tunes". Mike Stand of Smash Hits wrote: "Synthesisers and bubblegum go together like tinned peaches and Carnation, hence [Depeche Mode's] hit singles: melody, uncluttered electronics and nice voices in humanising harmony." Paul Morley of the New Musical Express described the album as "generous, silly, susceptible electro-tickled pop... that despite its relentless friskiness and unprincipled cheerfulness is encouraging not exasperating", noting the music's "diverting vitality", and concluding that "Depeche Mode, apparently, could quickly move... far up and away from constructing slightly sarcastic jingles."
Paul Colbert of Melody Maker felt that Depeche Mode speak with "a winning immediacy" and called the album "a wriggling giant of motivation, persuading each muscle to jump in time with the music", while at the same time criticising the presence of certain tracks such as "Nodisco" that "repeat earlier thoughts and feels without adding fresh views." Rob White, writing for the Christchurch Press, was less positive, calling the music on Speak & Spell "instant pop, instantly disposable, as precious as the gladwrapped swan on the... cover", remarking that the songs "would actually blow away in the wind... if it wasn't for their ability to chance upon melody hooks that drag you along without any real protest" and ultimately calling the album "tedious". The Village Voice's Robert Christgau dismissed the bulk of the album as "tuneful pap" that "crosses Meco (without the humble functionalism), Gary Numan (without the devotion to surface), and Kraftwerk (without the humor—oh, definitely without the humor)."
In a retrospective review for AllMusic, Ned Raggett described Speak & Spell as "at once both a conservative, functional pop record and a groundbreaking release", as well as "an undiluted joy." Nitsuh Abebe of Pitchfork said that the album endures "not as stylish futurism (not anymore) but as the happy noises of teenagers who believed it to be stylish futurism—and with a charming earnestness." In January 2005, Speak & Spell was included as an "essential" album in Mojo magazine's "Depeche Mode + the Story of Electro-Pop" special edition.