Being developed by Capcom, the core gameplay is similar to that of the Street Fighter series, incorporating elements such as Super Combos, as well as EX Attacks from Street Fighter IV. Players each choose two fighters from the Street Fighter and Tekken series, both sets of characters are controlled using the Street Fighter 6-button system, however it has been revealed that the Tekken characters will be able to perform Tekken style combos using the primary four buttons in a similar fashion to the Tekken 4-button system. These fighters can be switched out normally, or during certain combos. As fights go on, players build up power in a three sectioned meter at the bottom of the screen referred to as the "Cross Gauge", which allow the player to perform various techniques depending on how much of the gauge is filled, such as EX Attacks, Cancels, Super Arts and various Cross techniques detailed below. As opposed to the other crossover fighting games released by Capcom, in which the player must eliminate all the opponent's fighters to win, victory conditions are more similar to Tekken Tag Tournament, in which the first player to have one of their fighters' health bars reduced to zero loses the round, the player who wins the most rounds winning the match.
The tag team element of the game is heavily emphasized, with players being able to switch between the two characters in their team in a variety of manners. Switch Cancel allows players to switch partners in the middle of a combo, whilst Cross Rush combos involve launching the opponent into the air before swapping partners and continuing the combo. Cross Arts, which require a full Cross Gauge, allows players to chain together each character's Super Combo in one straight attack, whilst the Cross Assault mechanic allows players to simultaneously control both characters in their team until the Cross Gauge runs out.
Street Fighter X Tekken features two new game mechanics: the Gem System and Pandora Mode. Players equip up to three gems to their characters, which provide different stat boosts depending on the type of gem. Six varieties of gems exist: attack, defense, speed, vitality, assist, and Cross Gauge. Each gems and its effects are designated by a specific color, and will activate as the players fulfill certain conditions during battle. When a character on a player's team has less than 25% health remaining, that character can be sacrificed in order to activate Pandora Mode, which gives the remaining fighter increased strength and an infinite Cross Gauge. However, this state has a time limit and the player will automatically lose if he/she cannot defeat the opponent before the Pandora state runs out.
The game will feature various online options. Two players can battle on the same team, one controlling each character, and face off in four player matches. Scramble mode allows four players to fight simultaneously in pairs of two. The game will also support online training modes which can be played competitively or cooperatively with two players, as well as support the Fight Request feature.
Other Capcom games will be referenced in the game, such as Dino Crisis, which has a stage based around one of its levels.