American Express shares were barely down at $91.70 in after-hours trading.
Mr Chenault, who was widely expected to retire, spent the last two years firefighting after the company lost a lucrative partnership with warehouse club retailer Costco Wholesale Corp, which accounted for about 8 per cent of the spending on its cards.
The stock lost roughly a fifth of its value in 2015, after the deal ended. The breakup shook up the credit card industry, driving business from millions of customers to other card companies.
"He probably would have hung it up about two years ago and then he decided to stick through (after) all the bad news ... just to help them ride out that rough period," Kyle Sanders analyst Edward Jones said.
"I think Steve carries on with the strategies that Ken has already had in place; I wouldn't expect a major shift in how AmEx operates."
AmEx is also battling competition from US banks targeting its affluent clientele. Bank of America last month launched its Premium Rewards credit card, joining rivals JPMorgan Chase & Co and Citigroup.
Mr Chenault joined the company in 1981.
"Ken's been the gold standard for corporate leadership and the benchmark that I measure others against. He led the company through 9/11, the financial crisis and the challenges of the last couple of years," said billionaire Warren Buffett.
Mr Buffett's Berkshire Hathaway Inc is American Express' largest shareholder.
Separately, AmEx also reported a 19 per cent rise in quarterly profit, helped by loan growth and higher card member spending. The company raised its full-year 2017 earnings per share expectations to $5.80 to $5.90, from $5.60 to $5.80.
This is the first quarter without the impact of the loss of the Costco partnership.