David Cousin, 1854, S transept added 1862, N transept 1873, chancel extended 1921, vestry built on S side of church 1929. English Gothic style, gabled church; irregular square-plan but reads as approximate cruciform; whinstone with polished honey-coloured sandstone dressings and details; stugged margins. Plate and geometric traceried windows; hoodmoulds, label stops; low, saw-tooth coped, staggered angle buttresses; base course. Steeply-pitched roofs.
E ELEVATION: broad gabled nave at centre with transepts recessed to left and right, porches set in re-entrant angles. Deep base course, tall 3-light geometric traceried window at centre; honey-coloured shouldered gabled sandstone bellcote, cross finial. Window on right return; porch set in re-entrant angle to right, Tudor-arched door, (boarded with cast-iron hinges and handle), bipartite window to right; gabled porch on left return.
S ELEVATION: 1862, symmetrical M-gable transept, 2-light geometric traceried window, figurative water spout at centre (possibly re-used from earlier building); memorial plaque at ground of outer right gable. Gabled porch to outer right, pointed arch doorway. 1929 T-plan vestry block to outer left in re-entrant angle; canted-end memorial chapel aligned SW-NE, 2-light lancets; piend-roofed block projecting to S, cruciform arrowslit window; chamfered door to right.
N ELEVATION: 1873, M-gable transept, 2-light geometric traceried window to left, window to right 3-light with tracery replaced by pierced roundels (Oliphant stained glass window removed here in 1921 following enlarging of chancel). Tall gabled block, accommodating organ, recessed in re-entrant angle against chancel to right, coped apex stack; 2-light lancet on right return. Chancel with 3-light geometric traceried window at centre.
Leaded and stained glass windows. Grey slate roof, ashlar ridging, ashlar coping to skews.
INTERIOR: The interior with exceptional stained glass. Chancel rubble with dark wood dado, transepts painted, box-pew type seating. High, pointed chancel arch; stained glass chancel window serves as Rosneath and Clynder War Memorial, Stephen Adams, Glasgow; carving of Last Supper below window by Meredith Williams, donated by Princess Louisa 1931. Organ to right gifted by Princess Louisa in 1875, 2 Manual Tracker organ set on carved wooden casing made by Hills. Queen Victoria's bible rests on altar table, gifted by Princess Louisa in 1917; communion cups, 1585 AD by John Mosman, Edinburgh. At N side of chancel arch is St Modan's stone. Bell in N transept, taken from old church, inscribed 'Ian Burgerhuis me fecit 1610 Soli dei Gloria?; window in N transept donated by Mrs Oliphant, 19th century author, was former chancel window. Window to John Leod Campbell in E gable. 2 windows in S transept by Dr Douglas Strachan, 1908 and 1915. Former reredos of 10 commandments painted in cloth over wood now on E wall of S transept, by A Maitland 1862.