A significant part of Filkins's childhood was spent intensely studying classical guitar in Barcelona, Spain. Filkins attended Colorado Springs Christian High School in Colorado Springs, Colorado and played for the high school soccer team. There he met and became friends with bandmate Ryan Tedder during their senior year. During a drive home, as Filkins and Tedder were discussing their favorite musicians, they decided to put together a band. The two along with a few others played as 'This Beautiful Mess'. They had a couple of small gigs at Pikes Perk, attended by friends and family. Senior year ended and Tedder and Filkins parted ways, each attending different colleges.
In June 2010, Filkins and his wife, Lindsay, welcomed a son, Leighton Zachary. He openly thanked and acknowledged her in the liner notes of OneRepublic's debut album, Dreaming Out Loud. Filkins speaks fluent Spanish. In a local interview in Spain, he can be heard answering all the interviewer's questions in clear Spanish.
Before moving to Los Angeles and starting OneRepublic, Filkins did some modeling on the side in Chicago. He worked under Maximum Talent Agency and was featured in a few brands ads such as on Covington and Jockey Underwear. His torso image can still be seen on some packages of Jockey Underwear.
Filkins plays guitar and sings background vocals for the band. In addition to guitar and background vocals, he also aids friend and co-founder, Ryan Tedder, in writing and composing music for the band. Filkins shares writing and composing credits on the songs "All Fall Down", "Prodigal", "Say (All I Need)", "Sleep", "Something's Not Right Here", "Stop and Stare", "Tyrant" and "Won't Stop".
In 2002, Filkins got a call from Tedder asking him if he still wanted to put together a band. Tedder convinced Filkins to move to Los Angeles from Chicago. After a few line-up changes the band solidified with Tedder on keyboards and lead vocals, Filkins and Drew Brown on guitar, Brent Kutzle on bass and cello and Eddie Fisher on drums and percussion. After only nine months in Los Angeles they were signed to Columbia Records and recorded a full album, which took two years. Two months before the album was set to be released, they were dropped from the label. As soon as they were dropped, the band's MySpace profile took off and they soon became the number one unsigned act in the social networking site. A number of labels offered them a record deal including Interscope Records. Although hesitant to go under another major record label the band signed to Interscope under Timbaland's Mosley Music Group, as its first rock band.