Apple announced Thursday that it had elected Susan L. Wagner, a founder of the investment firm BlackRock, to its board. The longest-serving board member, Bill Campbell, is retiring, the company said.

The switch follows several recent changes at Apple, including the $3 billion acquisition of Beats Electronics and a major partnership with IBM announced this week.

Ms. Wagner will be the only member of Apple’s board from a company focusing on finance. Some other directors, like Robert A. Iger of Disney, Millard Drexler of J. Crew and Arthur D. Levinson of Genentech, work in industries that occasionally intersect with Apple’s business.

Apple said its retiring board member, Mr. Campbell, had been involved with the company since 1983, when he served as vice president for marketing. He joined Apple’s board in 1997, shortly after Steven P. Jobs returned to Apple as the company was near bankruptcy.

Ms. Wagner served in various positions with BlackRock, an investment company that now manages over $4.3 trillion, from its founding in 1988 until 2012 and still serves on its board. She earned her graduate business degree in finance from the University of Chicago.

“Sue is a pioneer in the financial industry, and we are excited to welcome her to Apple’s board,” Timothy D. Cook, Apple’s chief executive, said  in a statement. He added that Ms. Wagner would help in areas like mergers and acquisitions and expanding Apple’s business overseas.

In other words, Ms. Wagner will be important for Apple as it continues its transition from underdog in the PC era to industry leader in the smartphone era.