Geotechnical characteristics of the sediments from a known submarine slope failure at Kitimat Arm, British Columbia, are related to the results of geological and geophysical surveys. Site geology and morphology of the fjord, evaluated from high‐resolution side‐scan sonar and subbottom profile data, show the effects of at least three separate instability events. The geotechnical properties of the sediments involved in the instability processes have been analyzed from piston cores and cores collected from a manned submersible. Four distinct instability mechanisms are identified within the fjord, including failure of the fjord wall and delta‐front sediments, initiation of movement of fjord‐bottom clays, long‐distance translational movement on the low‐angle fjord floor, and block gliding at the downslope front of the landslide. Using post‐failure geometries and geotechnical data, factors such as coastal construction, tidally induced drawdown, and undrained loading are evaluated as possible initiators of sediment instability.