Embodiments of the present invention may include a variable nozzle turbocharger having a variable nozzle mechanism. The variable nozzle mechanism has a unison ring and a drive arm. The unison ring adjusts a degree of opening of variable nozzles having nozzle vanes through rotation of the unison ring. The unison ring has a first fit-engagement groove. The first fit-engagement groove has a closing side surface of a concave arcuate shape and an opening side surface of a convex arcuate shape facing the closing side surface with a fixed groove width therebetween. A drive arm has a first fit-engagement portion engaged with the first fit-engagement groove so that the first fit-engagement portion is rotatable and movable in the radial direction of the unison ring. The first fit-engagement portion has a closing side contact surface of a convex arcuate shape that is able to contact the closing side surface.