Stages in Project X Zone take place in grid-based locations from the game's many crossover titles. Each friendly unit is made up of two characters (thus referred to as a Pair Unit), though a third character (or "Solo Unit") can be added for once-per-battle assistance. Unlike Namco × Capcom, units can move freely within their range on the field map, with no penalty for accessing treasure chests or destructible objects prior to attacking.
The battle system is called the Cross Active Battle System, wherein pressing the A button in combination with the Circle Pad performs up to five basic attack combos. Additional gameplay elements include Support Attack, which allows the player to call in a nearby ally for assistance, and Cross Hit, which freezes the target in place during simultaneous attacks from multiple units. Also, the player can trigger Critical Hits by connecting their next attack just before the target hits the ground after the first. As the player's units deal damage, the player's Cross Power (XP) gauge fills up and can be used for special attacks and defensive moves on the map. Damage done via Cross Hits can fill this gauge up to 150%.
Project X Zone has a total of 15 save game slots included in the game, which can be used for recording a save game file during intermissions with a quick save file and a soft reset command.
Over 200 characters (allies and enemies, not counting event-only characters) were included in the game. It was confirmed that the overseas versions will feature the same character roster as the original Japanese version.
Kogoro Tenzai(天斎 小吾郎,Tenzai Kogorō?) is a detective who is a descendent from a ninja clan. He takes other jobs because so far detective work has run dry. Kogoro is a master of ninjutsu and is armed with a Nyoraitou which connects to another blade. He also has concealed wire blades attached to his feet. He is voiced by Toshihiko Seki.
Mii Kouryuuji(黄龍寺 美依,Kōryūji Mii?) is a high school student with a hot temper and a bit of a selfish personality. From a young age, she trained with a monk on how to use a giant gun called the Dragon Jewel and the Purple Pot pistol. She also has guns on her two boots, known as Tiger Heels. She is voiced by Yukari Tamura.
Namco Bandai came up with the idea of a "dream crossover" and brought on Capcom and Sega. The game was first revealed in a teaser by Bandai Namco on the official website until it was revealed in the May 2012 issue of Famitsu.
The initial creation of the characters were done in 3D character models before they were converted to be SD pixel art. Notable attacks used by the characters had to be done in 2D space in order to preserve its source material origin.
The game features two theme songs, with the opening song titled "Wing Wanderer" and the ending titled "GALAXY", which were both performed by Yoko Takahashi. The opening movie was created by the new animation studio Trigger, which was founded by former Gainax employees Hiroyuki Imaishi and others. In September 22, 2012, Katsuhiro Harada, producer of the Tekken series, has revealed on Twitter: "I proposed localization of Project X Zone." He added that the company has "not decided yet, but It will be realized if I continue proposing." Namco Bandai Games announced on January 21, 2013 that the game will be officially released in North America, Europe and Australia during summer 2013. The English versions of the game retain the Japanese voices, like Otomedius Excellent, though the vocals for the theme music were removed for legal reasons.
The game sold more than 85,539 units in its first week in Japan. In the west, the game has sold over ten times more than what Bandai Namco was expecting.  The game was among the 20 best games sold in the United Kingdom after it made its debut. In the United States, the game has been among the best selling games sold for the 3DS.
Project X Zone has received mixed to positive reviews from western critics. The game currently has a score of 70 on Metacritic.IGN's Scott Thompson gave Project X Zone a score of 8 out of 10, saying, "Project X Zone is often funny and consistently frantic – two traits not necessarily associated with tactical RPGs. Its story is confusing and the chapters slavishly follow the same repetitive formula, but the superb battle system makes repetition not just tolerable, but enjoyable." Game Revolution gave it a 3.5 out of 5, saying, "Despite the lack of depth and the repetition of combat, Project X Zone follows through as a tactical, humorous, preposterous romp through the best hits of video games. Even if you find the combat system strange, the streak of character cameos and the ridiculous number of hits that rack up with every battle will make any hardcore fan smile with appreciation. And if you're anything like me, that's hard to do." On a more negative note, GamesRadar gave Project X Zone a 2 out of 5, saying, "With the wealth of RPGs, and even great SRPGs, that have arrived on the 3DS in the last several months, it would almost be unconscionable not to recommend one of those games instead of Project X Zone. Fun combat and screaming Tekken characters can only take you so far."
Kotaku's Mike Fahey included Project X Zone in his top ten games of 2013. In 2014, Kotaku also included the game among "The 12 Best Games on the 3DS". That same year WatchMojo.com ranked the game fifth in their "Top 10 Crossover Video Games".