In One Card Wonder, each player receives a card with a wonder of the world and a series of supporting buildings. The multiple stages of the wonder must be built from the ground up, while the buildings can be constructed in any order. Players have four meeples and a personal stock of resources, and there is also a general stock of resources. The supply bag with resources is passed from player to player to indicate who the active player is.

During a turn you perform one of four actions. You may draw three cubes from the fabric supply bag, add two to your personal supply and place the others in the general supply. You may take all resources of one type from the general supply. (You may only have eight resources in your supply at a time, so if you have more than eight resources after drawing or taking, you must return some to the general supply.) You may build a level of the wonder or a building by paying from your stock; your workers mark individual buildings as you build them, unlocking skills.

Finally, you may sell pairs of matching goods to the supply in exchange for coins. Coins can be used as a wild resource, but they also appear at the cost of some miracles. Resources sold or used to build are returned to the supply bag.

In games with four or more players, players may also trade. Trading is done off-turn, that is, it can involve anyone except the active player. You may freely negotiate and trade with other players, but you must stop negotiating once you receive the supply bag and become the active player. The longer you spend on your turn, the more chance your opponents have to make deals.