The church stands back from Vauxhall Bridge Road (from which it would not originally have been visible when built) and lies parallel to the road.
It is constructed primarily from red bricks with an exterior embellished with black bricks, bands of Morpeth stone, voussoirs of coloured bricks and marble shafts.
The steeply sloping roof is covered with slate, with a gable at one end and carried round the apse as a half-cone at the other end.
The building is surrounded by cast-iron railings of Street's design, topped with wrought-iron crestings representing lilies.
These were a last-minute addition inspired by the design of railings which closed-off the chapels within Barcelona Cathedral's cloister.
They were made by James Leaver of Maidenhead in 1866.

A columned porch and passage leads out towards the street.
Above the porch is a free-standing tower reminiscent of an Italian campanile, an architectural feature that Street greatly admired ("there are no features of Italian buildings which are so universally remembered with pleasure").
The tower is topped by a spire whose bulk is emphasised by being corbeled out, giving the structure a somewhat top-heavy look.
The spire is of an unconventional design, starting as a pyramid before splitting into a central spike flanked by four spirelets.
Street had seen similar examples at Tournai in Belgium and at Genoa in Italy; it seems likely that he based that of St James the Less on the latter examples, which he described in a lecture delivered while he was working on the church.

The overall effect was quite unlike that of the traditional English church tower, but followed John Ruskin's prescription that "where the height of the tower itself is to be made apparent, it must be ... detached as a campanile" and "there must be one bounding line from base to coping."
Street later wrote that this "breadth of effect" was "the very point which northern architects were most careless to succeed" and which, by implication, he sought to deliver in his churches.
His tower at St James the Less was his most pronounced example of a free-styling campanile, though he built similar examples of solid, massive, freestanding towers at a number of other churches in England and Rome.

The church's interior has a broad aspect with three wide bays leading up to the apse.
The walls are dominated by red brick, which is contrasted with black brick, mastic and red and yellow glazed tiles which link the floor to the lower walls.
The nave is lined with short granite columns, each with carved capitals by W. Pearce, which support arcades of notched and moulded bricks.
The capitals are illustrated with carvings of parables and miracles.
At the clerestory end are three-light windows in the first two bays and plate tracery in the third.
The chancel is separated from the nave by a prominent arch.
Unlike the nave, it is groined in brick and is extensively decorated with mosaic and inlaid marble.
The design of the sanctuary thus makes it a distinctively darker and more elaborately mysterious area of the church.

Many of the church's interior features were inspired by the architecture of churches in France, Italy and Germany.
The columns and capitals reflect those of the chapter house and cloister of St-Georges de Boscherville near Rouen, while the vaulting is a reinterpretation of that in the church of St Jacques, Compiègne.
St-Pierre in Paris's Montmartre district provided further inspiration.

The fittings of St James the Less are mostly original and were part of Street's vision for the church.
A heavily carved pulpit was contributed by Thomas Farmer, though it is now somewhat battered.
In 1861 George Frederic Watts provided a fresco of the Last Judgement known as "The Doom" above the chancel arch.
He replaced it in the 1880s with a mosaic of Venetian glass made to the same design, after the original fresco had deteriorated.
The church's stained glass was designed by Clayton and Bell and depicts various saints, including its patron St James the Less.
The font is capped by an unusual domed iron canopy that was displayed at the 18
The church stands back from Vauxhall Bridge Road (from which it would not originally have been visible when built) and lies parallel to the road. It is constructed primarily from red bricks with an exterior embellished with black bricks, bands of Morpeth stone, voussoirs of coloured bricks and marble shafts. The steeply sloping roof is covered with slate, with a gable at one end and carried round the apse as a half-cone at the other end. The building is surrounded by cast-iron railings of Street's design, topped with wrought-iron crestings representing lilies. These were a last-minute addition inspired by the design of railings which closed-off the chapels within Barcelona Cathedral's cloister. They were made by James Leaver of Maidenhead in 1866.
A columned porch and passage leads out towards the street. Above the porch is a free-standing tower reminiscent of an Italian campanile, an architectural feature that Street greatly admired ("there are no features of Italian buildings which are so universally remembered with pleasure"). The tower is topped by a spire whose bulk is emphasised by being corbeled out, giving the structure a somewhat top-heavy look. The spire is of an unconventional design, starting as a pyramid before splitting into a central spike flanked by four spirelets. Street had seen similar examples at Tournai in Belgium and at Genoa in Italy; it seems likely that he based that of St James the Less on the latter examples, which he described in a lecture delivered while he was working on the church.
The overall effect was quite unlike that of the traditional English church tower, but followed John Ruskin's prescription that "where the height of the tower itself is to be made apparent, it must be ... detached as a campanile" and "there must be one bounding line from base to coping." Street later wrote that this "breadth of effect" was "the very point which northern architects were most careless to succeed" and which, by implication, he sought to deliver in his churches. His tower at St James the Less was his most pronounced example of a free-styling campanile, though he built similar examples of solid, massive, freestanding towers at a number of other churches in England and Rome.
The church's interior has a broad aspect with three wide bays leading up to the apse. The walls are dominated by red brick, which is contrasted with black brick, mastic and red and yellow glazed tiles which link the floor to the lower walls. The nave is lined with short granite columns, each with carved capitals by W. Pearce, which support arcades of notched and moulded bricks. The capitals are illustrated with carvings of parables and miracles. At the clerestory end are three-light windows in the first two bays and plate tracery in the third. The chancel is separated from the nave by a prominent arch. Unlike the nave, it is groined in brick and is extensively decorated with mosaic and inlaid marble. The design of the sanctuary thus makes it a distinctively darker and more elaborately mysterious area of the church.
Many of the church's interior features were inspired by the architecture of churches in France, Italy and Germany. The columns and capitals reflect those of the chapter house and cloister of St-Georges de Boscherville near Rouen, while the vaulting is a reinterpretation of that in the church of St Jacques, Compiègne. St-Pierre in Paris's Montmartre district provided further inspiration.
The fittings of St James the Less are mostly original and were part of Street's vision for the church. A heavily carved pulpit was contributed by Thomas Farmer, though it is now somewhat battered. In 1861 George Frederic Watts provided a fresco of the Last Judgement known as "The Doom" above the chancel arch. He replaced it in the 1880s with a mosaic of Venetian glass made to the same design, after the original fresco had deteriorated. The church's stained glass was designed by Clayton and Bell and depicts various saints, including its patron St James the Less. The font is capped by an unusual domed iron canopy that was displayed at the 18
St James the Less, Pimlico