Dislocation microstructures have been characterized by transmission electron microscopy in polycrystalline coesite deformed experimentally at 4 GPa, 1200 °C. Burgers vectors have been determined by large-angle convergent-beam electron diffraction. Sample orientation was assisted by precession electron diffraction to overcome difficulties arising from pseudo-hexagonal symmetry. The results are explained by using a pseudo-hexagonal setting. We found that most dislocations observed are of the ⅓〈21̅1̅0〉 type. No clear glide plane was identified, suggesting that climb is activated under these conditions. This conclusion is supported by the observation of numerous subgrain boundaries. We have also observed some  dislocations. Finally, the C12/c1 space group to which coesite belongs being centred, an additional slip system is observed: ⅙ [1̅21̅3] (011̅1) (½ [1̅10] (110) in the monoclinic setting).