Saltalamacchia, 30, became free to sign with any club after the Miami Marlins released him with more than $14 million left on his three-year, $21 million contract.
Saltalamacchia is to report to the team's spring training facility in Scottsdale, then will be sent to one of the Diamondbacks' affiliates, probably Triple-A Reno.
"I can't say he'll get so many at bats and he'll be here," Diamondbacks manager Chip Hale said before Thursday night's game against San Diego. "We'll assess what we have and what's going to make us better."
Saltalamacchia is a .240 career hitter with a .725 OPS in nine seasons with Atlanta, Texas, Boston and Miami. He had lost his starting job in Miami to rookie J.T. Realmuto and was hitting .069 (2-for-29) when the Marlins designated him for assignment last week.
Saltalamacchia is expected to get an opportunity to play in Arizona, where catchers Tuffy Gosewisch, Jordan Pacheco and Gerald Laird have hit a combined .219 with a .526 OPS in 96 at-bats this season.
The Diamondbacks had considered acquiring Saltalamacchia in a trade, Hale said, but the team is happy to have him as a free agent.
"When he became a free agent, we were interested, and I think he's interested in us, which is nice," Hale said. "He's interested in maybe the opportunity to play. Like I said before, we just have to see where we are when he's ready and how our guys are doing."
Information from The Associated Press was used in this report.