Pompey have sold almost 24,000 tickets after the first day of sales for their Checkatrade Trophy final against Sunderland.
Fans have been eager to snap up seats for the club’s first trip to Wembley Stadium since 2010, with more than 15,000 still available.
Chief executive Mark Catlin said: “It is no surprise that our fans have once again shown their fantastic backing for Kenny and the boys.
“That superb support is sure to be a boost to the team when they take to the pitch at Wembley, for what is sure to be a memorable day.
“We appreciate that fans have had to be patient with so many trying to buy over the phone and online, and are grateful for your continued backing.”
"It is no surprise that our fans have once again shown their fantastic backing for Kenny and the boys."
All season ticket holders and former shareholders can currently purchase up to six tickets per client reference number.
Seats for the contest on Sunday, March 31 (2.30pm kick-off) can be bought online here or by calling the Ticketmaster call centre on 0844 847 1898.
Phone lines are open between 8am-8pm from Monday-Saturday (8am-6pm on Sundays). Calls cost 7p from landlines, but charges from mobile phones may be considerably more.
Subject to availability, tickets will be available for general sale from 8am on Monday, March 18.