Growmi is a platformer with dungeon-crawl and slither elements. While enjoying a happy day on its own world, a bright yellow worm or snake, Growmi, is sucked through a portal into another dimension. In this strange land, it discovers that it has lost part of its length. The player helps Growmi regrow and return to its world by exploring mazes and solving puzzles.
The player can direct Growmi left, right, up, down and back upon itself. Additionally, they can direct it to push and lift standalone objects, such as crates and boxes, and interact with buttons to open doors. They also help Growmi collect a certain number of stars in the maze to receive a section of its original length.
The game features a map of previously discovered areas, which the player can access via a waypoint marker at the top left corner or shortcut key. The various areas house several feminine lifeforms that task the player with additional missions to complete, such as finding missing puzzle pieces and pearl earrings. After each mission, Growmi receives special abilities, such as teleportation between previously visited areas via the map, one-key shrinking of Growmi's body and a magnet on Growmi's tail that can attract and pull objects.
Although the game features spike pits, Growmi rarely falls into one because it's easy for the player to direct it to inch around obstacles and drop upon, hang from and stick to surfaces.