The concept was "based loosely on a short story" written by keyboardist Ken Hensley in June and July 1972.

[11] Village Voice critic Robert Christgau described the songs on the album as "third-hand heavy metal fantasies (...) hooked to some clean, powerful arrangements, and a good melody or two.

AllMusic reviewer remarked the album's prog elements and wrote that "The Magician's Birthday never quite hits the consistent heights of Look at Yourself or Demons and Wizards, but remains a solid listen for Uriah Heep fans".

[7] Joe Geesein of Record Collector praised the musicians and the good sound of the album's reissue, but wrote that most of the songs "don't stand up quite out so well" in comparison with opener "Sunrise" or the single "Spider Woman".

[10] Canadian journalist Martin Popoff called The Magician's Birthday "another colourful, mystical journey", although "somewhat disjointed, less accessible and in total much less metallic" than previous efforts, "culminating in the band's most harrowing, nightmarish epic of them all, the ten minute title track.