[7] When Harley was recording his debut solo album Hobo with a Grin in 1977, Bolan returned the favour by playing guitar on two tracks, "Amerika the Brave" and "Someone's Coming".

Writing for Record Mirror, Bolan commented in 1977, "The Beeb were not over anxious to play my last single and there was me thinking I had been clever by omitting the offending reference to cocaine on the album cut.

[18] On its release, Rosalind Russell of Record Mirror predicted "Dandy in the Underworld" would be a hit and wrote, "Three track throttle from an elf turned punk.

"[19] Charles Shaar Murray of New Musical Express felt the song was "the kind of over-solemn dog-spittle that Marc gets into when he feels important".

He added that the single's two B-sides were "unpretentious little rock pieces that ride around the turntable more than happily".

[20] In a retrospective review of the song, Dave Thompson, writing for AllMusic, considered it to be "a genuine Bolan classic".

As "one of Bolan's most honestly autobiographical songs in years", Thompson noted the "candid synopsis of his own decline" in the lyrics.

He noted the return of Bolan's "favourite C-Am-F-G chord sequence, majestically restated despite the cheesy, pomp rock synth" and how the lyrics saw him "revisiting Greek mythology".

[21] In a 2020 retrospective on the top 10 T. Rex songs, Brian Kachejian of Classic Rock History picked "Dandy in the Underworld" as number five on the list.

He considered the song to be "pure T. Rex excitement" and added that it "seemed to be a preview for the next musical chapter of Bolan's life until he was tragically killed".