Greg Nussbaum was born on August, 14, 1975, in St. Louis, Missouri. His father was a radiologist and his mother was a former special education teacher who stayed at home to raise him. In 1979, his brother, Scott was born in Tennessee. He grew up in Pittsburgh, Pennsylvania, and went to Shady Side Academy. He is a lifelong Pittsburgh Steelers and Pirates fan.

From an early age, Greg loved copying presidential biographies from the World Book Encyclopedia. He was fascinated by American birds, which he learned from his father, and was an avid collector of stamps, sports cards, and toys from super market vending machines. He played soccer and tennis. In 1994, Greg was accepted to Hamilton College in Clinton, New York, where he majored in psychology. In 1997, he met his future wife, Clara. That same year, he took a child development class at Hamilton and gained his first experience inside a classroom at Clinton Elementary School. Following college, Greg planned on becoming a children’s book author.

In 1999, Greg completed his Masters of Arts in Teaching at the University of Pittsburgh and was hired as a second grade teacher at Fairview Elementary School in Fairfax Station, Virginia. He quickly became a popular teacher for the fun games he invented with his second graders. While at Fairview, Greg bought his first HTML for Dummies book. HTML is the language used to make web pages. He was fascinated by HTML and began building mrnussbaum.com in 2003. At first the site was simply a way to post assignments and pictures of class activities for parents. When Greg realized that he could make many of the games he invented in the classroom into digital reality through web-based languages such as java script and software called Flash, everything changed. Cash Out, Tackle Math Ball, Coast to Coast, and GeoAmerica, were among the first games to be published on MrNussbaum.com. Greg came up with the concepts but hired Paul Burney, a web applications developer, to write the code and make the graphics. The games were big hits with his students and parents and soon word spread about mrnussbaum.com. In a few months, the site generated enough web traffic to attract advertisers. With advertising money, Greg started to hire programmers and graphic designers to make complex educational games such as Tony Fraction's Pizza Shop, Conquer the Continents, Genius Boxing, and eventually games such as the Lost Lunchbox and the Great American Multiplication Challenge. Meanwhile, Greg continued teaching and building the site's non-game content such as interactive maps, biographies, math drills, and reading comprehension exercises. In 2010, MrNussbaum.com achieved one million visitors in a month for the first time. It has become one of the world's most popular educational destinations for young students.

Today, MrNussbaum.com continues to grow and Greg continues to develop games and activities while teaching sixth grade full-time. He now teaches at White Oaks Elementary School in Burke, Virginia. He and Clara have two boys: William and Gabriel.