Deemer was born in Nashville, Tennessee, and grew up in London, England, attending Westminster School, and later Harvard University, where he received a BA Cum Laude in 1993. He went on to later study computer science at Stanford University.
Deemer started his career as an undergraduate, working for the Let's Go travel guides, where he served as editor of Let's Go: Europe, Managing Editor, and eventually Publishing Director of the entire series. After graduation, he joined PC World Magazine in San Francisco, where he helped launch of International Data Group's first online publications, PC World Online and Multimedia World Online. In 1996, Deemer left IDG to start GameSpot with two IDG colleagues, Vince Broady and Jonathan Epstein. In 2000, GameSpot was acquired by Ziff-Davis, which was in turn acquired by CNET Networks, where Deemer served as Senior Vice President of Outbound Media. GameSpot is now part of CBS Interactive, and is one of the leading videogames-related websites globally. In 2003, Deemer was hired as VP of Product Development for Yahoo!, and went on to become Chief Product Officer for Yahoo!'s emerging markets division, based in India and Singapore. In 2007, Deemer left Yahoo! to start GoodAgile, which now has operations in India, Singapore, and Sri Lanka, and is one of the best-known Agile consulting and training companies in Asia. In 2011 Deemer founded Stormglass Software, creator of the Stormglass Protocol series of young adult novels and iOS game, and he currently serves as CEO of both GoodAgile and Stormglass Software.
Deemer is the lead author of The Scrum Primer, one of the most widely read introductions to Agile software development, as well as The Distributed Scrum Primer. In 2012 Deemer was elected to the board of directors of the Scrum Alliance, where he chaired the Certification Committee between 2013-2015. Between 1995 and 2001 Deemer taught web development at UC Berkeley's Graduate School of Journalism, and between 2001-2003 he taught Internet business strategy at Berkeley's Haas School of Business, where he won the Club 6 teaching award. Since 2010, Deemer has been a visiting lecturer at the National University of Singapore's Institute of Systems Science, where he teaches agile project management.