St Mary’s Church 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. Every generation has updated the interior to suit the changing needs of the Church.

The Churchyard which surrounds the building encloses three and one-third acres. There are approximately 26,000 burials; 16,000 since the mid 18th C are recorded in the registers. There are over 1300 monuments, including four Grade II listed tombs, with the oldest legible monument dated 1710.

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 is in the style of 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.

The four Grade II listed tombs are: Wise (1710), Rigg (1754), Solly (1776) and Morley Wilson (1847). There are twelve Commonwealth War Grave Commission graves across the site. Many other fine monuments are to be found, some of which will be included in the Churchyard Trails.

The stories of people buried here across several centuries reflect the changing nature of society in Walthamstow; from rural Essex village to a place where City merchants and wealthy businessmen had their country residences.

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 England on glebe land opposite the church in 1828.

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

The churchyard is the second largest enclosed green space in the local area; many people have used it as a place of refuge and peace during the recent Covid pandemic. The churchyard is being managed to be a haven for wildlife and biodiversity and in 2021 was awarded a Silver-Gilt in the Churchyard category of London In Bloom.

Funded by the National Lottery Heritage Fund, work on renovating the ancient building began in 2021 and will run until the end of 2022. The aim is to regenerate Walthamstow’s oldest building, making it a working church, arts' centre, café, meeting space and education space. The changes to the building and church property will include an extension which will create an additional entrance into the building, plus church offices, art gallery and community meeting space; outside, the current car park will be turned into a landscaped public area for pedestrians to enjoy.

In the church itself, the pews have been removed, to be replaced with flexible cathedral-style seating which will drastically increase the number and variety of activities that can take place in the church. A new kitchen will be installed with a serving window for outside customers. The current entrance will be preserved; a new glass door will allow more light through while keeping the current door in place and open in the day for visitors.