Karen Fricker of Variety expressed the opinion that the musical had "remarkably high production value" but was too long. Fricker continued, "Jackson's hits sung by four strong-voiced, charismatic leads, backed by a crackerjack team of singer-dancers—is effective and entertaining". Sanjoy Roy of The Guardian observed, "It's cute, kicking and retro, but also highlights a danger that looms large in this show: that even as a tot, Jackson was supremely gifted performer—both as a singer and a dancer—and this tribute, however well intended, inevitably pales by comparison". Paul Vale of The Stage stated, "Those looking for history of Jackson's personal life should look elsewhere as this theatrical extravaganza is a breathtaking celebration of a musician whose work spans over three decades... Jonathan Park's set design and Nigel Catmur's lighting are complimented [sic] by LED screens creating some wonderful theatrical set pieces that are simple and yet remarkably effective". Benedict Nightingale of The Times said of one performer, "What [he] lacks in physical similarity to Jackson he also lacks vocally. The coarse, sandy qualities of his voice are as suited to "Rock with You" as custard is on a steak".
Charles Spencer of The Daily Telegraph commented, "Gary Lloyd, who doubles as director and choreographer, keeps the energy level at fever pitch almost throughout, and his dance routines, featuring daring leaps from an on-stage bridge, break-dancing, and, yes, the moonwalk, are spectacular. There is also a terrific band, ranging with aplomb from funk, soul and disco, through candy-rush pop to guitar-led rock". Malcolm Jack of The Scotsman noted that, "Some of Jackson's best numbers - "Don't Stop 'til You Get Enough", "Wanna Be Startin' Somethin'" and "Beat It" - were treated rather underwhelmingly, but the faithful(ish) to the video centrepieces - "Smooth Criminal", "Billie Jean" and "Thriller" - were fairly spectacular".
Amber Windsor of This Is Local London said of her experience at one show, "The signature high-pitched yee hee' echoed from the foyer and it was endearing to see a young boy recreating Michael's signature moonwalk, proving Jackson's music still appeals to all ages...The stage was vibrantly brought to life by the dancers, easily the strongest element of Thriller Live. Their endless energy and clear passion for the music reflected Jackson's own style". Mel Bradley of Dinnington Guardian recalled his enthusiasm and enjoyment while observing the musical, despite not being an "ardent fan of the king of pop". Julie Carpenter of Daily Express stated, "...this is a hugely enjoyable, gloriously upbeat, high-energy show which leaves you chanting Annie, are you OK? Are you OK, Annie? as you slip out the door".
Fiona Mountford of the Daily Mail noted that the script could have been written on "two pages of A4", but described the dancers as "astoundingly agile" and the show a "slick package".
On June 21, 2010, six performers in the London cast released Speechless as a single, to commemorate the one-year anniversary of Jackson's death. All proceeds from the recording were donated to the charity War Child.