The object of the game in Key Harvest is to score the most points. Players score points by placing tiles on their own country board. One point is scored for each field tile in the player's largest group of connected field tiles and two points for each tile in their second largest connected group.

Points are also scored for the worker tiles a player places on their country board. The number of points scored for each worker is equal to the number on the worker tile. Worker tiles do not count as connecting tiles when calculating the largest group of tiles. When played, a worker enables a player to take a special action. Each player has their own team of six workers, known as farmhands. There are also six townsfolk who can be acquired by any player.