Alex Seropian attended the University of Chicago and joined the Phi Delta Theta fraternity, where he met one of his future colleagues Jason Jones. Interested in computer programming, Seropian was pursuing a mathematics degree with a concentration in computer science as the Department of Computer Science did not offer undergraduate degrees at the time. He graduated in 1991 with a Bachelor of Science degree in mathematics. Before graduating, Seropian was living with his father, sleeping on his couch, and debating whether to get a job or create his own video game company. Seropian's father advised him to take a job to get experience, but the next day Seropian decided to found his own company. "My dad is a master of reverse psychology", Seropian said.

Seropian's first game was a self-published Pong-clone called Gnop! for Apple Macintosh. The game was free, although a few customers paid $15 for the game's source code. In 1991 he founded Bungie and published his first commercial game, Operation Desert Storm. Seropian sold 2,500 copies of the game, assembling the game boxes and mailing them out from his bedroom. Seropian partnered with his Artificial Intelligence classmate Jason Jones to publish Jones's nearly complete Minotaur: The Labyrinths of Crete; the game sold around 2,500 copies—it required a then-rare modem for network play—it developed a devoted following. After publishing Minotaur, the two formed a partnership.

For the next Bungie title, 1993's Pathways Into Darkness, Seropian hired a third team member for graphics work. The game was the first three-dimensional texture-mapped game on the Mac and the first true first-person shooter. By 1994 Bungie had grown to a staff of six and had moved into a rundown Chicago office—a converted former religious school located in front of a crack house. Their next title, Marathon, began development as a sequel to Pathways but grew larger. On release, it won several awards and established Bungie as the top Mac game developer.

For Halo: Combat Evolved, Seropian noted that the company had to incorporate new features such as surround sound and cinematics. Halo went on to sell more than 4 million units by 2004 and founded a media franchise encompassing sequels, books, and music. Seropian left Bungie in 2002 to spend time with his new family, but also due to frustrations with the game development process.

Seropian founded his own studio in 2004 called Wideload Games, intended to be more streamlined than most video game studios. Calling the method of game development "broken", Wideload began with a staff of 10, with the plan to outsource the lion's share of development, to stay within budget. Seropian said that the idea came from figuring out that his decades-old assumptions about how to make games did not necessarily apply to the future. Seropian turned to the film industry for cues, saying that it helped to look at an older industry that had been solving the same types of problems for a longer period than video games.^[ The external development model allowed Wideload to focus on the creative aspect of a project and added flexibility in what types of projects the team could take on. Wideload produced two games, 2005's Stubbs the Zombie in Rebel Without a Pulse and 2008's Hail to the Chimp.

On September 8, 2009, Disney acquired Wideload. Seropian joined Disney to head its in-house game development team, Disney Interactive Studios. The sale of Wideload was not originally planned: Wideload and Disney began working on a title together, and as conversations turned to a "broader scope and vision", the two companies "discovered [they] had a lot in common," Seropian said. Seropian left Disney in February 2012. Seropian also serves as DePaul University's second "game designer in residence"; DePaul is the first liberal arts university to offer a bachelor's degree for game design