Jahn–Teller (JT) distortion of the diamagnetic neutral divacancy (V20) in Si is studied by positron annihilation spectroscopy. Based on the anisotropy of electron momentum distribution around the divacancies obtained by two-dimensional angular correlation of positron annihilation radiation (2D-ACAR) technique, the preferred alignment of the divacancy in a specimen by compressing uniaxial stress along the [011] axis is detected. The direction of the alignment evidences the pairing JT distortion rather than the resonant bonding distortion, which is similar to the distortion in the singly negative divacancy (V2−).