Irvine-based accounting firms White, Nelson & Co. and Diehl, Evans & Co. have agreed to merge.

The combined firm will have more than 125 employees companywide, according to the company.

White Nelson employs about 80, all in Irvine. The firm ranked No. 11 on the Business Journal’s list of accounting firms, which was based on the number of local employees and published in July.

Diehl Evans employs about 45 people companywide, with more than half here. It ranked No. 34 on the list. The firm has two additional offices in Carlsbad and Escondido.

The name of the combined operation will be White Nelson Diehl Evans LLP.

It will operate from the White Nelson headquarters in Irvine starting in December.

Dave Doran, managing partner of White Nelson, will head up the combined firm.

Plans for an expansion push in San Diego County are under way, according to Doran.

White Nelson primarily serves industries such as manufacturing, financial services, healthcare and employee benefits.

Diehl Evans has focused on government, real estate and small business clients.

“The merger will allow us to further diversify into areas such as government and nonprofit, and create additional efficiencies in our business,” Doran said in a statement.