When encountered, Master Green attacks by skidding across the ground and jumping around, eventually producing sparks from his body (like a Sparky), shooting sparks at Kirby, or sending an electric shock wave across the ground. He always slides or jumps before the shock. After the shock wave, he throws an electrical star towards Kirby that explodes, which he can inhale and exhale back at Master Green. He can also jump into the air and throw stars from above.
Master Green is a big jellyfish imbued with electricity. His head is disc-shaped with two small black eyes. From beneath his head, eight thick tentacles hang down. The official artwork depicts him as yellow, despite his name. In the Kirby of the Stars Pilot, however, he was green with greenish-blue tentacles. Although he is a jellyfish, he shares more traits with cephalopods than cnidarians. Master Green is also not transparent like regular jellyfish.