The original Norman Church was built in around 1070, and the central Norman tower still remains, with its massive stone blocks and characteristic rounded arches. The Church is reputed to be the oldest building in Southampton. Isaac Watts' parents and sister are buried here and the Old Tournai Font (1170)

Throughout the Middle Ages until the dissolution of the monasteries in 1536 St Michael's was in the patronage of St Denys Priory, which had been founded in 1127 by Henry I.

The church was originally cross-shaped, but in the late 14th Century the North Aisle was widened. In the 15th Century the South Aisle was similarly widened and the West Door rebuilt.

A spire was constructed at this time, although the present one dates from 1878

The last substantial alterations were made in 1826-8 when the Nave was heightened and cast iron pillars installed. Some alteration was also made to the Chancel later in the 19th Century.

The stained glass is mostly recent, replacing that damaged by bombing. The East Window depicts the five churches that were once within the old walled town. The West Window depicts St Michael slaying the dragon.