Ermington gave its name to a Hundred and there was probably a church on the present site from Norman times, although it would have been much smaller than the present one.

There is some Norman stonework between the porch and the present tower but there was only a single central aisle and a lower chancel than there is today, as can be seen from the roof plates above the Choir stalls.

In the 14th century, the Norman tower was demolished and a new one built where it still is, but without a spire.  The north and south aisles were also added and, in the 15th century, the Lady Chapel and spire were built.  The North Transept was added in the 16th Century.