A millimetre-wave radar is tested in an INRAE experimental unit to monitor sow postural activity in presence of her piglets. A total of 16 sows of the Large White breed with piglets aging from 7 to 15 days are monitored inside farrowing pens with measurement sequences lasting 2 to 3 hours at different dates. The radar is attached to the farrowing pen entrance at a distance to ground of 1.8m, and the sow’s position is remotely estimated from the backscattering of electromagnetic waves. The radar-based detection technique does not require equipping animals with radiofrequency tags. The automatized system records 3D images are built from the simultaneous azimuth (digital) and elevation (mechanical) radar beam scannings with a time resolution of 3 seconds. By applying an algorithm based on Constant False Alarm Rate, undesirable radar echoes from the pen are mitigated and only radar detections of the sow are recorded over time. A clustering algorithm is applied to the detections to obtain the 3D position of the sow. A classification of sow postures is performed from a Quadratic Discriminant Analysis of the 3D positions. Ground-truth postures of sow are annotated manually from video recordings. The two following classes of postures are finally analysed: the ‘standing and transition’ and the ‘lying’ classes (‘transition’ refers here to both ‘sitting’ and ‘kneeling’ postures). The training data is composed of radar detections of 4 sows for the total monitoring duration of around 8 hours, or equivalently for 7,097 detections. The tested data is composed of 34,356 radar detections of 12 other sows for a total monitoring duration of 38 hours. The precision and sensitivity are 88.3 and 90% for the ‘standing and transition’ class, and 97.9 and 98% for the ‘lying’ class. Precision and sensitivity of the classification may vary from one sow to another due to the difficulty to classify correctly ‘transition’ postures for some of them. Based on these first encouraging results, future work will be devoted to further develop the radar detection method, and detect the motion of the sow according to changes in her location in the pen.