Mraz was born and raised in Mechanicsville, Virginia. He is of Czech and Slovak descent through his grandfather, who moved to the United States from Austria-Hungary in 1915. His surname is Czech for "frost". (Czech: mraz)

On July 26, 2005, Mraz released his second major label album, Mr. A-Z, produced by Steve Lillywhite for Atlantic Records. The album's lead single, "Wordplay", was produced by Kevin Kadish, and entered the Billboard 200 at number 5. The album earned a Grammy Award nomination for Best Engineered Album, Non-Classical, while Lillywhite received a nomination for Producer of the Year.  Mraz began a long-running tour in support of Mr. A-Z at the San Diego Music Awards on September 12, 2005. The tour featured several opening acts, including Bushwalla and Tristan Prettyman, with whom he had written the duet "Shy That Way" in 2002. Mraz opened for Alanis Morissette during her 2005 Jagged Little Pill Acoustic tour, and for the Rolling Stones on five dates during their 2005-06 world tour. In March 2006, he performed in Singapore as part of the annual Mosaic Music Festival. That May, he toured mostly small venues and music festivals in the U.S., along with a few shows in the United Kingdom and Ireland where he supported James Blunt  The tour included a May 6, 2006 acoustic show with P.O.D., Better Than Ezra, Live, and The Presidents of the United States of America. Mraz was featured as a headlining guest of St. Louis's annual Fair St. Louis and performed a free concert at the base of the Gateway Arch on July 1, 2006. During this time, Mraz was also the opening act at several dates for Rob Thomas' Something to Be Tour.  In 2005, Mraz was one of many singers featured in the fall advertisement campaign for The Gap entitled "Favorites", singing a cover of Bob Marley's "One Love". 2006 saw the release of Selections for Friends, the live, online-only album recorded during the Songs for Friends Tour. In 2007, "The Beauty in Ugly", an earlier track penned by Mraz originally titled "Plain Jane", was rewritten for the ABC television show Ugly Betty. The song was featured as a part of ABC's "Be Ugly in '07" campaign. Also that year, on American Idol, contestant Chris Richardson performed a cover of Mraz's "Geek in the Pink".

which president did he support?