Americans are saving more of their paychecks than at any time since February 1995, a shift toward thrift that could prolong the recession but strengthen the financial health of U.S. households and the overall economy if it lasts.

Even as income grew, personal saving as a percentage of after-tax income rose to 5.7% in April, the Commerce Department said Monday, up from 4.5% in March and well above the zero savings rate reported a year earlier.

The...