When Edward III founded his new college at Windsor in August 1348 he attached it to a 13th-century chapel constructed by Henry III in the lower ward of the castle. St Edward's Chapel, as it was then known, was immediately rededicated to the Blessed Virgin Mary, St George and St Edward and remodelled as part of the construction of the new college. Between 1350-3 its roof was extensively repaired, the interior reglazed with painted glass and a set of new stalls erected for the canons. Finally, in 1367 a massive altarpiece of alabaster was made at Nottingham by Master Peter the Mason and brought to Windsor in ten carts, each drawn by eight horses. Of this first chapel little now survives but the present Albert Memorial Chapel probably stands on the footprint of its foundations. A hundred years after the foundation of the college the present chapel was created for the devotions of the community.

In 1475 Edward IV set in motion a hugely ambitious redevelopment of St George's funded with French money received under the terms of the Treaty of Picquigny. The centrepiece of this redevelopment was a chapel of cathedral-like proportions set out immediately to the west of its predecessor. Integral to the new building was the king's own funeral monument and chantry. The construction of this sumptuous chapel, one of the masterpieces of late medieval European architecture, was supervised by Richard Beauchamp, bishop of Salisbury, and directed by the master mason Henry Janyns. This new building completely obscured the original public façade of Edward III's college and necessitated a complete reordering of the lower bailey, including the construction of the Horseshoe Cloister for the community of the vicars. Finally, Edward IV effectively re-founded the college as an incorporated body and by Christmas 1482 had settled its constitution with 45 junior members: 16 vicars, a deacon gospeller, 13 lay clerks, 2 clerks epistoler and 13 choristers.

When Edward IV died his new collegiate church and funerary monument were far from complete. The choir was roofed but not vaulted and the walls of the nave were still under construction. Despite the king's death, work to the chapel does appear to have continued for a short while but the Yorkist defeat at the Battle of Bosworth in 1485 soon brought operations at St George's to a complete standstill. Just before this event, however, the body of Henry VI, the Lancastrian king murdered by Edward IV was brought to the chapel. Almost immediately miracles were reputedly worked by the murdered king and a pilgrimage cult focused on Windsor began to develop and with far-reaching results.

In 1493 the Tudor king Henry VII began to consider the question of where he should be buried and, drawn by the reputation of Henry VI, eventually determined on Windsor. To create a suitable burial place he pulled down most of the old chapel of St George and began a new Lady Chapel on the site. By 1498 this was all but vaulted and then the situation suddenly changed - it was determined in a law case that Henry VI had actually desired burial in Westminster Abbey. It was directed, therefore, that his body be moved from Windsor to Westminster. Confusingly, the body never was actually translated but Henry VII did begin a second funeral chapel at Westminster instead in expectation of the move. This was the Lady Chapel now popularly known as the Henry VII Chapel and it gives some impression of the sheer ambition of Henry VII's unfinished designs for his Windsor mausoleum.

But although Henry VII now lost interest in St George's and left the Lady Chapel unfinished, two of his close friends ensured that building operations did not grind to a halt. Dr Christopher Urswick, a canon and later Dean of Windsor, supported by the wealth of Sir Reginald Bray, a Knight of the Garter from 1501, began to complete the main chapel. Between 1498 and 1509 the entire interior was vaulted in stages with the exception of the crossing, which was intended for a lantern tower. By 1528, however, this plan was abandoned and the crossing also vaulted. Since this time the only material addition to the building has been the construction of the King George VI Memorial Chapel at the junction of the choir and north transept, designed by George Pace.

But despite this continuity the building has changed appreciably. Early drawings of the exterior also show that each transept originally had a small cupola above it. The transepts were also originally without buttresses, features added in the 20th-century restoration of the building and which detract slightly from the soaring delicacy of the design. Internally there have also been several major restorations, most notably in the late eighteenth century by Henry Emlyn. Under his direction several major alterations were undertaken including the reordering of the stalls in the choir and the construction of the present fine choir screen and organ.

In the 19th century Queen Victoria made some important changes to the arrangement and furnishing of the chapel. In devotion to the Prince Albert she reworked the east end of the choir. She also completed the Lady Chapel abandoned by Henry VII as his burial place. Under the direction of Gilbert Scott the interior was vaulted and richly furnished, a magnificent royal mausoleum at last after a delay of more than three hundred years. Finally, in 1872 a set of steps was erected at the west end of St George's Chapel to create a ceremonial entrance to the building.