In the present work, we have investigated the stable configurations, electronic, and magnetic properties of the functionalized boron nitride (BN) nanosheets by NHx (x = 0, 1, and 2) groups by performing comprehensive density functional theory (DFT) calculations. The results indicate that these groups can be stably incorporated into BN nanosheet, resulting in the formation of covalent bonds between these adsorabtes and BN sheet. The adsorption energies of the most stable configurations are − 2.80, -2.42, and − 0.33 eV, respectively, for the adsorption of N, NH, and NH2 groups on BN nanosheet. The electronic structures of BN nanosheets are found to be effectively modified by these groups due to the introduction of certain impurity states within the band gap of the pristine BN nanosheet, thereby reducing the band gaps in various ways. The relationship between the electronic structures and the configurations of these functionalized BN nanosheets is also addressed by exploring the projected density of states combined with charge transfer analysis. In particular, the attachment of the N and NH2 groups renders BN nanosheet exhibit magnetic nonzero magnetic moment, contributed mainly by the N atoms of adsorbates. The present results are expected to open a way to change the electronic and magnetic properties of BN nanosheet, which is helpful to design or develop novel nanodevices based on BN nanosheet.