St Mary’s started as a 12th C Norman building, built around 1108 as a manorial church by Ralph de Toni, son of the standard bearer of William the Conqueror. It is the oldest building in Walthamstow and stands at the heart of the first conservation area in the London Borough of Waltham Forest, Walthamstow Village. For over 900 years, the church has been at the centre of faith and community in Walthamstow.

The building has been much altered over the centuries: aisles were added to a basic rectangular church in the 13th C, the tower was rebuilt in 1535, two 16th C chantry chapels were absorbed into the side aisles in the 19th C, galleries were added in 18th & 19th Cs, the East wall was pushed back in 1938 due to a major crack in the existing wall, the south gallery was removed following bombing in WWII and the chancel was opened up in 2001.

There are five brasses, one 15th C and the remainder from the 16th C. Mounted on a column, one of these is a fine brass memorial to Sir George Monoux (died 1543) and his wife, Dame Mary. He was a significant benefactor of the church and local community, where adjacent almshouses and a nearby local sixth form college still bear his name. There are also two palimpsest brasses.

The earliest stone monument was erected in 1601 by Sir Edward Stanley in memory of his wife, Lady Lucy. The sculptor is thought to be William Cure II, later Master Mason to King James I.

The Merry monument of 1633 was intended by Sir Thomas Merry (a prominent Royalist) as a joint memorial to his wife and himself; the sculptor was Nicholas Stone, Master Mason to King Charles I, and the verses are said to have been written by Sir William Davenant the Royalist poet.

The Trafford monument, erected in 1689, is the largest and most imposing monument in the church and can be convincingly attributed to Grinling Gibbons.

Designed by James Humphries Hogan, the five lancet East Window, a memorial to Sydney Harris, dates from 1939 and is the work of James Powell & Sons (Whitefriars) Glassworks.

William Morris, the founder of the Arts & Crafts Movement was baptised in the marble font in 1834.

Samuel Pepys is known to have attended services at St Mary's on two occasions and to have drunk ale with Sir Wm Penn and Sir Wm Batten at the church stile in the churchyard.

Rev William Wilson, vicar 1822-1848, a pioneer of infant education, erected the first purpose built C of E Infants' School in the country on glebe land opposite the church in 1828.

The tower has a peal of ten bells which were refurbished in 2016. On a clear day, the panoramic view from the top of the 19m tower takes in many landmarks including Epping Forest, the O2 Arena, the Olympic Stadium, the Shard, Canary Wharf, Crystal Palace transmitter, Alexandra Palace and more.

In the last twenty years, Tudor beams were exposed in the tower porch and Georgian timbers in the South Porch.

St. Mary's Churchyard which surrounds the building encloses three and one-third acres; of the approximately 26,000 burials, 16,000 since the mid 17th C are recorded in the registers. There are 1246 monuments with the the oldest dated 1710.