Ultimate Wildmutt is significantly larger and more muscular than Wildmutt. His fur is a maroon-red color.
His chin is much larger and his quills are gone, and have been replaced by 4 huge gray spikes on the back of his neck. He now has a small tail with a gray spike on the tip of it. His teeth are now slightly larger. His claws and teeth are now gray.
Unlike original Wildmutt, Ultimate Wildmutt gains the ability to speak English, which is the result of its evolution. He also has black outlines over his lips, like Wildmutt from the original series.
He has gained a long controllable tail with a scorpian style stinger at the edge, its function aside from stabbing is unknown. He is stronger than Wildmutt, with longer claws and he could hold down the prisoner while his regular form couldn't. He has also removed a weakness of his original form,as now he can talk. He is also much larger than the original Wildmutt, this advantage gives the Ultimate Wildmutt the ability to tackle larger enemies with much less effort.
- Strangely, Ultimate Wildmutt did not appear in the episode The Ultimate Sacrifice, despite being an Ultimate Form.