The Diamondbacks selected Barnhart's contract Monday.
The transaction confirms that Barnhart will be a part of the Diamondbacks' Opening Day roster, which had already been made apparent when his primary competition for the No. 2 catcher role, Jose Herrera, was optioned to Triple-A Reno on Sunday. During his time in the big leagues with the Reds, Tigers and Cubs, Barnhart has been valued for his defensive work and ability to handle a pitching staff, but the Diamondbacks aren't likely to count on him to make more than one or two starts per week while top backstop Gabriel Moreno is healthy.