The new location is a cooperative venture between the $37 billion-asset banking company and Family Savings Bank, the largest African-American-owned institution in California.
Family Savings, a community-oriented thrift with $174 million of assets, will send customers with commercial banking needs to Comerica's office next door.
The new operation will deal in lines of credit and conventional and Small Business Administration loans for small and midsize businesses.
Comerica, in turn, will direct customers with retail banking needs to Family Savings.
"Comerica Bank has no credibility yet in this area, but through this alliance we get a strong linkage to the market right off the bat," said J. Michael Fulton, the president and chief executive officer of Comerica's California unit. "We've entered Los Angeles on a much more novel and running-start basis than we thought we'd be able to."
Comerica has 31 offices in California, with $4.6 billion of assets. It is also negotiating a lease for a full-service branch in downtown Los Angeles, Mr. Fulton said.
The five-county Los Angeles area has one of the most vibrant economies in the nation, yet it has not been the headquarters of a major banking company since 1996, when Wells Fargo & Co. of San Francisco bought First Interstate Bancorp.
Among the region's banking leaders are Wells Fargo, Bank of America Corp. of Charlotte, N.C., and Washington Mutual Inc. of Seattle.
Smaller institutions such as City National Corp. of Beverly Hills, with $6.3 billion of assets, have developed an expertise similar to that of Comerica, which generally focuses on relationship-style banking for firms with annual sales ranging from $1 million to $150 million.
"We will have a low share here, but we focus on being one of the best relationship-based banks," Mr. Fulton said. "Our template is skill, not scale."
Joseph K. Morford, an analyst with Dain Rauscher Wessels in San Francisco, said building business in the area will not be easy for Comerica, but that the strategic alliance with Family Savings will help.
"With big banks and community banks targeting business clients, it's a very competitive market," Mr. Morford said. "They have found a creative way to break into the market."
"Comerica does exactly what we would if we had the resources," said Family Savings president Wayne-Kent Bradshaw.
To keep up its side of the bargain, Comerica agreed to restrict its office to making loans. The office will be headed by Donald Kincey, formerly a vice president at the Los Angeles-based foundation WattsHealth System, which owns 70% of Family Savings.