The device connects a first end-coupler with a second end-coupler, in particular of a piping. A nut is provided with a threaded bore in which the first end-coupler is screwed along a longitudinal axis. In a tightening position, the first end-coupler is in axial stress with a second end-coupler accommodated in the nut. Anti-rotation means are provided between the nut and at least one of the end-couplers to prevent relative rotation except when a torque exceeding a predetermined threshold is applied thereto. The anti-rotation means consist of at least one tab made in the material of the nut to lockingly interfere with substantially planar faces formed on the second end-coupler.