The Old Customs House is a two-storey building constructed by Giuseppe Bonnici in 1774 by the water's edge at Xatt Lascaris. The walls are massive and in some places are as much as four metres thick. The façade on the lower level is constructed in coralline limestone, whereas the upper level is built in globigerina limestone.

The main façade has a central bay with pairs of attached pilasters raised on plinths flanking the arched entrance, above which is an open balcony.

Flanking the central bay are two wide bays with three windows each at both ground and upper floors. All windows are square-headed; those at ground level have a plain moulding around them, while the upper ones have triangular pediments on top of them with the central ones on either side having a segmental pediment. A continuous cornice separates the lower and upper levels of the façade. The side façade is similar to the side bays with three identical windows.

A near-life-size, franka stone statue showing St Publius stands on the right-hand corner of the Customs House and was recently restored by the Valletta Rehabilitation Project.

Mepa scheduled the Old Customs House and statue of St Publius as Grade 1 national monuments as per Government Notice No. 276/08 in the Government Gazette dated March 28, 2008.