A power tool comprises an adjustable auxiliary handle assembly that facilities safe use of the tool by the operator when handling heavy duty handheld machinery. The adjustable auxiliary handle assembly comprises a strap, a handle base, an over-center linkage assembly, a locking lever, a locking lever and an adjustable knob. The strap is easily released and able to rotate and be locked in a different position convenient and comfortable to the operator. The auxiliary handle assembly is adjustable and can be operated with one hand (e.g., one-handed operation). The over-center linkage assembly holds the auxiliary handle position in place while allowing the power tool to be used in high-torque/high load applications.