The invention relates to a Coriolis flow sensor. The sensor comprises a housing and at least a Coriolis-tube with at least two ends being fixed in a tube fixation means. The flow sensor comprises excitation means for causing the tube to oscillate, as well as detection means for detecting at least a measure of displacements of parts of the tube during operation. According to the invention, the Coriolis flow sensor comprises a reference mass, as well as further excitation means arranged for causing the reference mass to oscillate during operation, as well as further detection means for detecting at least a measure of displacements of the reference mass during operation. Additionally, control means are provided for controlling the excitation means and/or further excitation means based on vibrations measured by the detection means and/or further detection means. This way a Coriolis flow sensor with active vibration isolation is obtained.