Arians said in a statement: "I never thought it was going to come. I appreciate it so much. I will give it every single thing I have. The passion and energy I bring to this is something I love to do.
"There is so much excitement. The more I got to meet with everyone here the more I got excited for the opportunity. I knew it was the right fit for me."
Quarterback Kevin Kolb added: "I've heard great things about Bruce Arians, not only as a coach but as a person. I look forward to working with him and winning a lot of games."
Arians was the offensive coordinator with the Indianapolis Colts this season, but spent much of the year as interim head coach while Chuck Pagano received medical treatment.