Naast de de standaard modi, zal Street Fighter X Tekken gebruik maken van het gem systeem. Dit zijn gems (DUH) die allemaal hun eigenschappen hebben en je kan toewijzen aan je karakter. Om het systeem in balans te houden heeft elk voordeel ook zijn nadeel, dus je zal goed tactische moeten overwegen hoe je de gems gaat gebruiken.

A brand new feature that combines customization with strategy, the GEMs add an extra level of depth and provide a pioneering way to experience fighting games.

A total of 57 GEMs (5 Assist and 52 Boost) come standard in Street Fighter X Tekken. Players have the ability to equip three different GEMs that improve upon weaknesses or capitalize on strengths to enhance their inherent play style. The two types of GEMs, Assist and Boost, each have specific advantages and disadvantages.

Players can select any combination of the Assist GEMs, which provide helpful bonuses that are always activated but balanced by handicaps in other areas. Conversely, Boost GEMs provide a stat increase in one of five areas (attack, defense, speed, cross gauge, vitality) but require a specific condition to be met in order to be activated. As an example, a particular speed Boost GEM will be activated automatically after a player blocks 2-3 stringed attacks from their opponent. As GEMs are assigned prior to a match, the activation conditions for the Boost GEMs are hidden from opponents, promoting an element of surprise that requires players to think and act quickly.