Early episodes of the anime are aired in a different order than their corresponding chapters in the manga: Meat arrives in the first episode, Kinnikuman stays on Earth rather than going to Planet Kinniku (although he eventually does so later on)
Certain names were changed, including: Abdullah→ Abdoodoollah, Beauty Rhodes→ Beauty Rorodes, Wolfman→ Rikishiman and others. This was done to avoid legal dispute with the real-life wrestlers who used these names (Abdullah the Butcher, Dusty Rhodes, Chiyonofuji Mitsugu, and others). Some move names were changed as well, like: Niku Curtain→ Kinniku Guard and Apache War Cry→ Wild War Cry (Scramble for the Throne only).
Robin Mask's skin color was changed from flesh-colored to blue, the skin is actually a body suit he wears as evidenced in the anime where he had flesh-toned skin when not wearing his armor. Conversely, Asuraman's was changed from blue to flesh-colored.
In the manga, the announcers eventually fade into the background until there's just one and he's only represented by speech bubbles appearing in the corners of the panels. In the anime, however, the announcers are always seen. Also, the color commentator Hiroshi Tazahama is replaced by Kazuo Nakano.
The more violent scenes have been toned down. For instance, the infamous scene in the first Olympics where Ramenman rips Brockenman in half with the Camel Clutch has been changed to him merely chopping Brocken's back and then turning him into ramen noodles which he then eats.
Instead of soiling his pants at the Camel Clutch, Kinnikuman is turned into noodles... and then brought back to life with garlic.
The American Tour Arc only covers the fight with Jesse Maivia to the rematch with Robin Mask. The Tag Tournament and the second Monster Extermination saga is scrapped completely.
Originally, Kinnikuman meets Bibimba and they fall in love, causing Kinnikuman's first love interest, Mari Nikaido, to leave Japan. After the series ends, Kinnikuman and Bibimba get married. In the anime, Mari stays around as Kinnikuman's main love interest with Bibimba only playing a very small role in the final storyline.
In the manga there are very obvious hints that Mongolman is actually Ramenman in disguise (such as Mongolman removing his mask and fake upper-body muscles while walking off into the distance). In the anime these hints are missing.
La Niang was found and raised by Mapo's Troupe instead of the old carpenter.
The character Banboro only appears once in the manga, but in the anime he makes numerous appearances and joins Gundam and Chuchai as one of Ramenman's allies.
The character Quancao is introudced before Hogan, unlike in the manga.
In the first episode, Kinniku Mantaro is sent to Earth and awakens Meat, whereas in the first chapter of the manga Bone Killer (renamed Blood Killer in the anime) attacks him on Planet Kinniku, and Meat is awakened after the Hercules Factory training. Also, Meat takes Ramenman's role in the episode.
Kinniku Suguru is shown as missing for several years in the first episode, whereas in the manga he is shown as still being with Mantaro and Bibimba on Planet Kinniku
In the manga, Mantaro finishes Tel-Tel Boy with the Mantaro Bomb, while in the anime he uses the Kinniku Buster
In the manga, Kinniku Mantaro was blackmailed by Sunshine into being the referee for the match between Terry the Kid and Rex King because he went to a topless galbi bowl shop. In the anime, Sunshine blackmailed him because Mantaro simply ate at a fish restaurant and couldn't pay the bill.