The warning comes amid forecasts that the U.S. economy is likely to slow this year, and possibly head into recession within the next few years.
New York-based JPMorgan's loan growth will slow to an estimated 2.4% in 2019 and 2.2% in 2020 from 4.2% in 2018, the KBW analysts wrote in a report.
"Our loan growth forecast reflects our view of economic growth slowing which should cause a decline in credit demand," the KBW analysts wrote.
JPMorgan is scheduled to report first-quarter results on Friday, and analysts with the Wall Street firm Goldman Sachs warned in a recent report that the biggest U.S. banks likely suffered an average 11% decline in trading revenue during the period.
So any reduction in lending revenue could put additional pressure on earnings.
According to KBW, JPMorgan's loans probably increased an an annualized pace of 2.6% in the first quarter, down from 4% in the fourth quarter.
"For JPM, slower growth is driven by a slower growth rate for wholesale loans and seasonality in the cards business," wrote the analysts, led by Brian Kleinhanzl.
The brokerage firm cut its estimates of JPMorgan's 2019 earnings per share to $9.51 from $9.55, below Wall Street analysts' average estimate of $9.70 for the year.
A JPMorgan spokesman declined to comment.
In an annual letter to shareholders published last week, Dimon said he doesn't expect a recession anytime soon. And whatever the case, he wrote, he doesn't worry too much about loan growth; it's just an expected feature of the regular business cycle.
"We do not worry about loan growth," the CEO wrote. "It is most definitely an outcome of how we manage credit and client decisions. We will not stretch, ever, to show growth in loans."
To Dimon's credit, the bank survived the 2008 financial crisis in better shape than nearly all of its Wall Street competitors -- an indicator of both its size and financial strength as well as risk management.
And indeed, it can be smart for banks to rein in their lending -- and tighten underwriting standards -- when an economic slowdown is brewing. That way, the lenders avoid holding loans that may quickly sour as household finances deteriorate and business sales slump.
So Dimon might be leading the way in lending, rather than falling behind.