Prominent architectural historians have criticised St Mark's Church.
 Nikolaus Pevsner wrote of its "terrible stone facing", while Harry Stuart Goodhart-Rendel considered both St Mark's and the very similar Christ Church (now demolished) to have "deplorable architecture [...] combining the smugness of the chapel [with] the peculiarity of the Gothic".
 The building does not reflect ecclesiastical architectural norms of the mid-19th century, partly because its construction started several years earlier and also because Reverend Elliott and the Marquess of Bristol held traditionalist, old-fashioned views.

The church was built in the Early English Gothic Revival style using a combination of concrete, stone and ashlar.
 The concrete was used to imitate Kentish Ragstone; the north side is stuccoed to resemble ashlar; and genuine ashlar was used for the late 19th-century extensions.
 The concrete section has stone quoins at the corners.
 The south façade, facing Eastern Road, has lancet windows and small buttresses, and the north face is identical.
 The tower, topped with a spire, stands at the west end and also has lancets and corner buttresses; it is flanked by porches.
 All roofs are of slate.

As originally designed, the nave and its adjacent aisles consisted of one open-plan area demarcated by narrow cast iron columns and piers.
 A stone chancel arch led to W. Gilbee Scott's chancel, with one bay and a window with tracery work.
 The vestry was on the north side of the chancel, opposite the organ chamber.
 The galleries, altered and mostly removed during the 1891–1892 work, originally ran round three sides of the interior and were held up by fluted columns.
Prominent architectural historians have criticised St Mark's Church.  Nikolaus Pevsner wrote of its "terrible stone facing", while Harry Stuart Goodhart-Rendel considered both St Mark's and the very similar Christ Church (now demolished) to have "deplorable architecture [...] combining the smugness of the chapel [with] the peculiarity of the Gothic".  The building does not reflect ecclesiastical architectural norms of the mid-19th century, partly because its construction started several years earlier and also because Reverend Elliott and the Marquess of Bristol held traditionalist, old-fashioned views.
The church was built in the Early English Gothic Revival style using a combination of concrete, stone and ashlar.  The concrete was used to imitate Kentish Ragstone; the north side is stuccoed to resemble ashlar; and genuine ashlar was used for the late 19th-century extensions.  The concrete section has stone quoins at the corners.  The south façade, facing Eastern Road, has lancet windows and small buttresses, and the north face is identical.  The tower, topped with a spire, stands at the west end and also has lancets and corner buttresses; it is flanked by porches.  All roofs are of slate.
As originally designed, the nave and its adjacent aisles consisted of one open-plan area demarcated by narrow cast iron columns and piers.  A stone chancel arch led to W. Gilbee Scott's chancel, with one bay and a window with tracery work.  The vestry was on the north side of the chancel, opposite the organ chamber.  The galleries, altered and mostly removed during the 1891–1892 work, originally ran round three sides of the interior and were held up by fluted columns.
St Mark's Church, Brighton