Mark Casady is stepping down as chief executive of LPL Financial Holdings Corp. after a decadelong stint, as one of the biggest brokerage firms continues to wrestle with regulatory problems and sweeping changes to how investors save for retirement.

Boston-based LPL, which provides services to more than 14,000 independent brokers, said Mr. Casady will be succeeded by Dan Arnold, the firm’s president since 2015, on Jan. 3. Mr. Casady will continue to act as LPL’s chairman until March 3 to advise Mr. Arnold in his early months at the helm.

In an interview with The Wall Street Journal, Mr. Casady said he felt this was an appropriate time for a transition with big industry changes ahead, including the Labor Department’s fiduciary rule requiring brokers to work in the best interest of retirement savers. It will force sweeping changes on the brokerage industry, affecting some $3 trillion in retirement assets, from how retirement savers pay for investment advice to how brokers are compensated.

“I had two choices: Retire now knowing you got a great leader in Dan in place or stay and see it through that phase,” Mr. Casady said. “My view is it is the right time to go.”

News of Mr. Casady’s departure follows the October disclosure that LPL is considering strategic alternatives, which are being led by Goldman Sachs Group Inc. and could include a sale of the company. Messrs. Arnold and Casady declined to comment on the review process.