Trump told the story of a policeman who he said thanked the president for making him look like a "financial genius" to his wife because of his 401(k)'s performance.
"Said he was up now 72%. I said that's not bad. ... He hugged me, he actually wanted to kiss me but I said, 'No, thank you,'" Trump joked.
"Many of you have 401(k)s, but does anybody in this room have a 401(k) that's down? Raise your hand," the president said, appearing not to see any raised hands.
"Does anyone have a 401(k) that's up? Everybody," he said as the crowd erupted into cheers and applause.
"I don't know what you would have had to do to get a 401(k) that's down," the president said.
Fidelity Investments found several reasons to be optimistic about 401(k) savings in its latest retirement savings report. The average 401(k) balance increased slightly in the second quarter of 2019, and the number of people with $1 million or more in their 401(k) increased to a record 196,000.
Monday marked the president's first visit to the city since taking office. He owns a Trump Hotel and Tower in the city.
The annual chiefs of police conference calls itself "the largest and most important law enforcement event of the year."