A vortex-sensing fluid flowmeter has a freely rotatable vortex-shedding body suspended in a section of conduit through which a fluid stream passes, the body being oriented generally transverse to the direction of fluid flow. The body has an integrally formed upstream-facing portion adapted to shed a series of vortices within the fluid, which vortices alternately influence opposite lateral faces of the body, tending to produce a periodic rotation of the body about a firmly attached rotational shaft. The shaft is rotatably mounted to the conduit and passes at one end through the wall of the conduit to the exterior thereof. A sleeve-like tube surrounds the shaft and is fastened tightly at its bottom end to the shaft and at its top end to the conduit wall to provide a fluid-tight seal around the shaft. The tube is sufficiently flexible and pliable to exert negligible restraining force against the rotation of the shaft. A sensing device located outside of the fluid stream and coupled to the externally protruding portion of the shaft exerts a predetermined restraint on the shaft. This restraint limits the maximum rotation of the shaft at high flow rates, for minimizing the fatiguing stress exerted on the sealing tube, yet does not impede rotation at low flow rates. The sensing device responds to the restrained rotations of the shaft, and electronic circuitry associated with the sensing device converts the response to a signal output indicative of the flow rate of the fluid.