Dimon and his family intend to sell 1 million of the 8.6 million shares they own, subject to the terms of a stock trading plan, the bank said in a regulatory filing on Friday.

Based on Thursday's closing price, the sale would fetch nearly $141 million, and their remaining stake be as big as $1.07 billion. The bank has a market capitalization of over $409 billion, according to LSEG data.

The sale is intended for "financial diversification and tax-planning purposes" and Dimon "continues to believe the company's prospects are very strong," the bank said.

He also continues to have unvested performance share units and stock appreciation rights, JPMorgan added.

Shares of JPMorgan dipped 0.7% before the bell, while peers Bank of America, Citigroup and Wells Fargo were marginally up.

Forbes estimates Dimon's net worth to be around $1.7 billion.

During his tenure at the biggest U.S. bank, Dimon has steered it through the 2008 financial crisis. He also orchestrated a rescue deal for First Republic Bank earlier this year, after it failed in May as an industry turbulence led to deposits spiraling out of control.

So far this year, JPMorgan shares have risen 5% and massively outperformed the S&P 500 Banks Index, which has declined 15.3%.