Shares of HP Inc., which sells printers and computers, rose 13% to $13.81 at 2:07 p.m. in New York, giving the company a market value of $24.8bn.
Meanwhile, shares of Hewlett-Packard Enterprise Co., which sells servers, storage devices and services, dropped 1.6% to $14.49, giving the firm a market value of $27bn.
HP is betting that the split will help the two new companies compete better in a fast-changing landscape for gear and services.
Shares of the original HP stock surrendered 33% this year through Friday. Revenue fell 8.1% to $25.3bn in its latest quarter, compared with analyst projections for $25.4bn, according to data compiled by Capital IQ. Sales have declined for 15 of the past 16 quarters.