On Assignment Inc. on Monday said it has acquired HealthCare Partners Inc., a regional physician-staffing firm based in suburban Atlanta, for more than $15 million.

On Assignment is a Calabasas company that specializes in health care and engineering placements. It operates 90 branch offices in the United States, Canada and overseas, including in the United Kingdom and China. HealthCare Partners has 41 employees and makes physician placements in 14 specialties across 24 states. Founders Ruddy and Rhonda Polhill are expected to stay with the company.

The deal includes a two-year earn-out opportunity of up to $3.7 million for HealthCare Partners’ owners.

HealthCare Partners is not affiliated with Torrance’s HealthCare Partners, Southern California’s largest network of physician groups.

On Assignment, which is scheduled to report second quarter earnings on Wednesday, will use a combination of cash on hand and borrowing under its senior revolving credit facility to pay for the acquisition. The company expects after-tax savings of about $450,000 per year over the next 15 years by classifying the acquisition as an asset sale.

HealthCare Partners will become part of On Assignment’s Vista Staffing Solutions unit.

“The acquisition will increase Vista’s size and the sub-specialties it serves, and will bolster Vista’s presence in the southeast region of the United States,” said Chief Executive Peter Dameris in a statement.

Shares closed down 5 cents, or less than 1 percent, to $10.15 on the Nasdaq.