The church is colloquially known as Saint Gregory's due to a traditional procession held on the first Wednesday following Easter Sunday.

[1] Its dedication to Catherine of Alexandria dates back to an original chapel on this site, which was one of the eight mother churches on Malta.

[5] The church is a Grade 1 scheduled building and is listed on the National Inventory of the Cultural Property of the Maltese Islands.

[6] The present-day road runs from St. Catherine's old church along the spine of the ridge, towards Xrobb l-Għaġin, before climbing the knoll of Tas-Silġ and descending to Marsaxlokk.

This is not the most efficient route for the transportation of bulk commodities from Żejtun to the bay, and may have been shaped by historic considerations, such as linking the Roman villa with Tas-Silġ.

[8] In the 19th century, historians linked the foundation of the church with the expulsion of the Arabs, following Count Roger's presumed raid in 1090/91.

[9] These links betrayed attempts to pre-date the veneration of St. Catherine of Alexandria with the Byzantine-Greek community living on Malta prior to the Muslim invasions of the 9th century.

[12] In any case, by the 14th century, a small early medieval chapel[13] dedicated to St. Catherine served the south eastern region of Malta.

The old chapel's façade, however, was turned northwards - as is a statue of St. Gregory just outside the church grounds - and faced the Cathedral of Mdina, the old medieval capital in the centre of the island.

The small and primitive medieval chapel served as the parish church of Żejtun for a long period of time.

All the lands making up today's Żejtun, Ħaż-Żabbar, Ħal Għaxaq, San Ġorġ ta’ Birzebbugia, Marsaxlokk, Delimara, St. Thomas' Bay and Marsascala, as well as a number of other small villages and lost hamlets, all fell under the parish's direct responsibility.

[14] By 1470, the church building had become a recognised national and international landmark and shrine, with sailors commending themselves for the saint's intercession: "God help us and St. Catherine of Malta.

Pietro Dusina in 1575, Gian Francesco Abela noted how the Cathedral precentor drew around 500 scudi in annual income from the lands belonging to St. Catherine's Old Church.

[21] The main façade has a Renaissance doorway, with flanked by a set of pilasters crowned by an architrave, a cornice and a circular oculus in the masonry above.

A small bell-cot, probably added later and constructed out of reused stones, rests on the gable, which straightens out on each side with a low parapet wall.

The buttress supporting the transept's walls, however, is larger and far older - giving the eastern side of the church the appearance of a fortress.

[24] High within the walls of the transept, a corridor was inserted with windows lined up on the sites of two new low lying forts, which were to be built at St. Thomas, Marsascala, and St. Lucian in Marsaxlokk.

Hence, St. Catherine's old church became an intermediate military signalling point, forewarning Mdina, Cottonera and Valletta about any attack by Ottoman navy ships entering these nearby ports.

On July 6, 1614, an Ottoman force of sixty ships (including 52 galleys) under the command of Khalil Pasha[25] tried to land at Marsaxlokk Bay, but were repelled by the artillery from the newly constructed St. Lucian Tower.

The attack is described in a commemorative plaque engraved close to the main altar of the church, which states that:"In the early hours of Sunday, July 6, 1614, a Turkish army landed from 60 galleys, disembarking six thousand men in the place called Ghizira in Saint Thomas’ creek.

Preventive protection works included the replacement of crumbling stone, the clean up of the front, the removal of the cement cover on the lower parts of the façades and re-pointing to avoid water seepage.

These coat-of-arms are not contemporary with the two different church buildings dedicated to the St. Catherine, as the first name listed, that of precentor R. Bartholomeus Asciach, served between 1372 and 1391, centuries before the sacristy was built.

[30] In April 1969, local newspapers reported the finding of a large number of human bones, and three secret passageways which were uncovered by workmen.

[34] The discovery took place when three workmen, Ċikku Żammit, Carmelo Spiteri and his sixteen year old nephew Grezzju Vella were waterproofing the church's vaulted roof.

Vella was working near the flat dome of the church and unwittingly began to scrape at a narrow crack between two stone slabs.

After the last discovery, the parish priest traced a certain Carmelo Zahra who confessed that he had entered the passages when he was a young boy together with some other individuals.

[35] The origin of this feast was unknown for centuries, with the common belief that it related to a general vow by the populace on their deliverance from a great plague in 1519.

[36] Recent studies have concluded that the procession was first held in 1543 by Bishop Domenico Cubelles, in response to a papal call for prayers for peace.

[35] Grand Master Perellos built a palace in Żejtun, on the main road from Tarxien, to attend the feast on the occasion of the annual procession.

In 1926, Bishop Mauro Caruana ended the participation of other parishes after arguments erupted between the clergy of Birkirkara and Isla, on the order of precedence in the procession.