The team has called a 3 p.m. PT news conference at PETCO Park to announce the hiring.
Garfinkel, who previously was the D-backs' executive vice president and chief operating officer, resigned from that post Saturday.
Garfinkel oversaw the business side of things for the D-backs, including marketing, ticket sales, corporate partnerships and sales. Before joining the Diamondbacks in 2006, Garfinkel was the executive vice president of the Chip Ganassi Racing Teams.
Garfinkel's departure from Arizona was not unexpected because he was brought to Arizona by then D-backs CEO Jeff Moorad, who took over last month as the Padres new vice chairman and CEO.
When Moorad resigned in January in order to purchase the Padres, there was strong speculation that that Garfinkel would join him in some capacity.
Corey Brock is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.