The deuteration mechanism of molecules in the interstellar medium is still being debated. Observations of deuterium-bearing species in several astronomical sources represent a powerful tool to improve our understanding of the interstellar chemistry. The doubly deuterated form of the astrophysically interesting amidogen radical could be a target of detection in space. In this work, the rotational spectrum of the ND_2_ radical in its ground vibrational and electronic X^2^B_1_ state has been investigated between 588 and 1131GHz using a frequency modulation millimeter/submillimeter-wave spectrometer. The ND_2_ molecule has been produced in a free-space glass absorption cell by discharging a mixture of ND_3_ and Ar. Sixty-four new transition frequencies involving J values from 2 to 5 and K_a_ values from 0 to 4 have been measured. A global analysis including all the previous field-free pure rotational data has been performed, allowing for a more precise determination of a very large number of spectroscopic parameters. Accurate predictions of rotational transition frequencies of ND_2_ are now available from a few gigahertz up to several terahertz.