On January 13, 2017, Iannetta signed a one-year, $1.5 million deal with the Arizona Diamondbacks.
On May 13, 2017, Iannetta was hit by a pitch from Johnny Barbato. Iannetta suffered a broken nose along with four fractured teeth, and required stitches on his lips.
On December 8, 2017, the Rockies and Iannetta agreed to a two-year contract, bringing the catcher back to Colorado. On August 13, 2019, Iannetta was designated for assignment.