Nine Men's Morris is played on a board by two players who take turns. The game starts with the board empty. Players take turns placing pieces on any empty intersection. After all eighteen pieces have been placed, players take turns moving. A move consists of sliding a piece along one of the board lines to an adjacent intersection. The players start with nine tokens each. In the first phase, opening, players place their tokens on any of the available slots on the board. When all tokens are placed, the game enters the second phase. Players now move their tokens. A token can be moved from one slot to another along the lines. Tokens can never be placed or moved to a slot that's already occupied.

Whenever a player forms a mill (three tokens in a row), they can take an opponent's token that doesn't belong to a mill. If all of the opponent's tokens are inside some mill then an exception is made and the player can take any token. In the opening, it's possible to form two mills by placing a single token. The player still gets to take only one of the opponent's tokens.

The game is won by bringing the opponent to a position where they cannot move, or by reducing them to only two tokens.

If a player has only three tokens left, they are allowed to move a token to any free slot.

The players may agree to a draw if they have a position where no player may reasonably win.