CHAPTER TITLES: 1. New Worlds To Conquer; 2. The Living Dead; 3. Queen of Magic; 4. Ancient Enemies; 5. The Boomerang; 6. Treemen of Mars; 7. Prisoner of Monga; 8. Black Sapphire of Kalu; 9. Symbol of Death; 10. Incense of Forgetfulness; 11. Human Bait; 12. Ming the Merciless; 13. Miracle of Magic; 14. Beasts at Bay; 15. An Eyes For An Eye.

BBC broadcasts of the first chapter, "New Worlds to Conquer", in the UK in the 1970s, 1980s and 1990s omitted the sequence where Happy Hapgood calls at Dr. Zarkov's residence and speaks to his African-American manservant, due to the racial stereotypes.

The bullet car used by the Clay People is the same one used in the scenes on Saturn in Buck Rogers (1939).

Much of the background music was originally used in Bride of Frankenstein (1935). Also, the song that played in the background during the sequence recapping the previous chapter's events was the theme for The Invisible Man (1933).

This was the final appearance of Jean Rogers as Dale Arden.

The serial debuted in March of 1938, just seven months before the infamous Orson Welles' "War of the Worlds" Halloween broadcast. To cash in on the controversy caused by the radio show, the studio edited the serial into a feature film, Mars Attacks the World (1938), and released it to theaters in November of that year.

The title of this serial was originally going to be "Flash Gordon and the Witch Queen of Mongo." It was changed so that Universal could save money by shooting the outdoor scenes on the back lot and not have to build costly sets, and by reusing the set for Emperor Ming's palace.

In the stock footage from Flash Gordon (1936), shown in this film, as Flash is telling The Clay People about his previous encounter with Emperor Ming, Ming is bald and Dale Arden has blond hair. In this sequel, Ming has "pasted on" hair and Dale is a brunette. It has been reported that Jean Rogers (Dale Arden) had many other film roles pending at that time (1938) that called for her to be a brunette.

This was the final appearance of Richard Alexander as Prince Barin.

King Features Syndicate released the three Flash Gordon serials as well as Buck Rogers (1939), Red Barry (1938), Ace Drummond (1938) and other comic strip cliffhangers to US TV in 1951. Because the television show Flash Gordon (1954), starring Steve Holland (I) as Flash, was in syndication in late 1953, the three Universal Pictures "Flash Gordon" theatrical serials were retitled for TV broadcast. Flash Gordon (1936) became "Space Soldiers", Flash Gordon's Trip to Mars (1938) became "Space Soldiers' Trip to Mars" and Flash Gordon Conquers the Universe (1940) became "Space Soldiers Conquer the Universe". To this day both the three original "Flash Gordon" serial titles and the three "Space Soldiers" titles are used.

Many of the original 1938 prints were dyed green.

Buster Crabbe (Flash Gordon), Charles Middleton (Ming the Merciless) and Frank Shannon (Dr. Alexis Zarkov) are the only actors to appear in all three "Flash Gordon" serials.

Swedish censorship #58.222. Universal Pictures in Sweden in 1938 showed this at the cinemas as a single 76-minute movie, not as a serial.