Abstract Recent results of fueling experiments in the GAMMA 10 tandem mirror using neutral beam injection are described. Neutral beam injectors (NBI) have been installed at the anchor-cells and central-cell for this purpose. Both anchor and central NBs are injected into a standard ICRF-heated hot-ion-mode plasmas and the increase of the electron line-density by 27% in the central-cell and 110% in the east anchor-cell is observed. Hα line-emission measured near the beam line of NBI indicates the enhancement of the neutrals in the periphery region of the beam line, which suggests the influx of cold gas from the ion source of NBI and the increase of hydrogen recycling due to the beam injection. An analysis of neutral particle transport using the DEGAS simulation code is developed to be able to calculate the spatial profile of neutral density in non-axisymmetric region. Detailed measurements of Hα line-emission from the central-cell to the east anchor-cell show the increase of particle source rate due to NBI and the obtained value occupies the total ionization rate by 29%.