The pilots are trying to increase the pressure on Lufthansa in negotiations over an early retirements scheme.
The proposed strike on Tuesday will run from 0700-1500 GMT, the union said. There will be no flights from Lufthansa's main hub Frankfurt and no long haul flights using Airbus A380, A330 and A340 planes, and Boeing B747s.
Germany's flagship carrier, which had called on the pilots to return to the negotiation table, said the strike announcement was disproportionate and that it would present a revised offer during the day.
While it would be no new offer, it would provide more details of an early retirement package, Lufthansa said.
Lufthansa shares fell 1.3 percent, making them the second-biggest loser on the blue-chip index Dax, which was trading 0.3 percent lower.
Vereinigung Cockpit, which represents about 5,400 of Lufthansa Group's 9,000 pilots, wants Lufthansa to maintain a scheme that allows pilots to retire early at the age of 55 and still receive up to 60 percent of their pay before regular pension payments start.
They held a strike at Lufthansa's budget carrier Germanwings at the end of August, followed by walkouts at Frankfurt and Munich in the past two weeks.
Pilots at rival Air France began a one-week strike on Monday over company plans to cut incentives.