Unlike other Super Sentai series, the monsters Bioman fight do not start small and become giants when defeated. Instead, Gear uses the five Beastnoids, recurring mechanical monsters that fight the Biomen at normal size. Beast King is Monster's underling, and while the other members of Big Three sometimes display a preference for a certain Beastnoid, he is the only one to be designated a "master". In episode 31 and in the movie, all five Beastnoids are present and perform their very own roll-call, similar to the Biomen led by Beast King.
- Psygorn (サイゴーン, Saigōn?) - A three faced psychic monster with the ability to spew fire and uses telekinesis and teleportation. He is the mightiest of all five as he caused serious problems to the Biomen in battle. He was at first working with Farrah but as time passed, he became Mason's closest ally where he also took part in killing Mika Koizumi after the Bio Killer Gun was empty in battle, although he was with Farrah when the latter confronted Mika in episode 2. Later upgraded with energy beams and stronger fire powers. He is rivals with Red One, Blue Three, Yellow Four II and Pink Five. He is the last Beastnoid to be killed and was destroyed by heavy damage caused by Red One and the Biomen, while trying to protect Mason of which he told the latter to get away.
- Mettzler (メッツラー, Mettsurā?) - A one-eyed spy monster with the ability to fire plasma bolts, turn into plasma and create holograms. Farrah's preferred Beastnoid, he is a cunning and dangerous opponent who uses deceptive tactics like his mistress though he also works for Mason as well when he first appeared. He is later upgraded with the ability to stretch his limbs at the same time Farrah was upgraded. He is rivals with Red One, Green Two, Blue Three and Yellow Four 2. Destroyed after an overdose of bio killer energy from Silva and receiving the bio electron charge attack while trying to shield Farrah. English version is: Plasmanoid
- Beast King (ジュウオウ, Jūō?) - He is a gorilla-like monster. Rather clumsy and scatter-brained, he is often there for comic relief and generally works along Monster. He is seen in episode 13 rescuing Monster after Messer Beast was defeated in battle. He survived the first attack and later fell down with parts still intact for reassembly. He was rebuilt for his loyalty at the request of his master with chest cannons. He works as the acting leader in the movie. He is rivals with Red One, Green Two, Blue Three and Yellow Four. Destroyed after receiving heavy damage from Silva and the Biomen. English version is: Zeroid
- Aquaiger (アクアイガー, Akuaigā?) - He is a water monster who uses a spear-gun and is armed with Bubble Bombs and Acid Spray. Works with Farrah and Mason most of the time, though he worked with Monster during the camera mission. He is probably the weakest of the group, and occasionally gets picked upon by the others for his incompetence which is seen in episode 14, where Monster kicked him down the ladder and was given a beatdown by the other beastnoids. Destroyed in episode 31 presumably with no spare parts. He is rivals with Red One, Green Two, Yellow Four 1, Yellow 4 2 and Pink Five. English version is: Aquanoid
- Messer Beast (メッサージュウ, Messājū?) - He is a gargoyle-like monster with the ability to fly and armed with supersonic waves and laser energy beams. Works with Farrah and Mason most of the time(with farrah in episode 9 and mason in episode 1), although at one point worked with Monster in episode 13. Destroyed in episode 31 presumably with no spare parts. He is rivals with Red One, Green Two, Blue Three and Yellow Four 2. English version is: Falconoid