The National Union of Journalists decided earlier this week to go ahead with the strike after it rejected Express Newspapers' offer of a 3% pay rise. The union said the offer was made without proper negotiation.
Despite the strike action, a Daily Express spokesperson said the paper "would definitely be out tomorrow".
It is believed the company has brought in freelance journalists to cover for those on strike.
This action is the first of three planned 24-hour strikes by the Express Journalists. It comes on the same day as the NUJ's Annual Delegates' Meeting in Belfast.