A process and device for estimating the vertical speed of a rotary wing aircraft may include integrating the sum of: (1) a first component corresponding to a vertical acceleration measurement and (2) a second component obtained from the difference between: (a) a first value incorporating a barometric measurement and (b) a second value incorporating a previous estimation of the vertical speed. The second component is derived from the difference between the first and second values by clipping this difference to eliminate, as appropriate, the part of the difference which is greater, in absolute value, than a predetermined value.