Any specific card game imposes restrictions on the number of players. The most significant dividing lines run between one-player games and two-player games, and between two-player games and multi-player games. Card games for one player are known as solitaire or patience card games. (See list of solitaire card games.) Generally speaking, they are in many ways special and atypical, although some of them have given rise to two- or multi-player games such as Spite and Malice.

In card games for two players, usually not all cards are distributed to the players, as they would otherwise have perfect information about the game state. Two-player games have always been immensely popular and include some of the most significant card games such as piquet, bezique, sixty-six, klaberjass, gin rummy and cribbage. Many multi-player games started as two-player games that were adapted to a greater number of players. For such adaptations a number of non-obvious choices must be made beginning with the choice of a game orientation.

One way of extending a two-player game to more players is by building two teams of equal size. A common case is four players in two fixed partnerships, sitting crosswise as in whist and contract bridge. Partners sit opposite to each other and cannot see each other's hands. If communication between the partners is allowed at all, then it is usually restricted to a specific list of permitted signs and signals. 17th century French partnership games such as triomphe were special in that partners sat next to each other and were allowed to communicate freely so long as they did not exchange cards or played out of order.

Another way of extending a two-player game to more players is as a cut-throat game, in which all players fight on their own, and win or lose alone. Most cut-throat card games are round games, i.e. they can be played by any number of players starting from two or three, so long as there are enough cards for all.

For some of the most interesting games such as ombre, tarot and skat (card game), the associations between players change from hand to hand. Ultimately players all play on their own, but for each hand, some game mechanism divides the players into two teams. Most typically these are solo games, i.e. games in which one player becomes the soloist and has to achieve some objective against the others, who form a team and win or lose all their points jointly. But in games for more than three players, there may also be a mechanism that selects two players who then have to play against the others.