An assisted opening folding knife having a blade with an engagement surface extending generally radially outwardly with respect to the pivot axis of the blade. A cantilevered leaf spring contacts the engagement surface and immediately urges the blade to the extended position upon the blade pivoting through a predetermined angle from the retracted position. An elongated engagement member is pivotally connected to the handle and configured for pivoting between a blade locking position and an unlocking position. In one embodiment, the cantilevered leaf spring also urges the engagement member towards the blade locking position. The engagement member automatically locks the blade in the extended position, and the cantilevered leaf spring, the blade, and the engagement member all substantially extend in the pivot plane.