Abstract: A tool for inserting O-rings into a recess provided in a bore in a part comprises a cylindrical housing having a cylindrical O-ring stripper rigid therewith and projecting from one end thereof. A plunger is reciprocably mounted within the housing for movement along its axis from a resiliently balanced, equilibrium position. An O-ring holder includes a pair of bars pivotally coupled to one end of the plunger and projecting from the housing through a notch dividing the stripper into two halves. The holder bars are each provided with a notch or jaw, with the latter being spaced for gripping an O-ring at diametrically opposite locations. An O-ring guide is reciprocably mounted to the plunger and extends between the two holder bars. A spring normally holds the guide for movement with the plunger but permits the guide to retract within the plunger when an O-ring is being picked up by the holder bars.