Plant species diversity, composition and dominance are important entities in understanding vegetation types. The wood plant species include; trees, shrubs, and woody climbers (lianas/vines). The study was conducted at Mahungu Green Belt Forest Reserve (MGBFR) in 2015 to investigate the woody plant species diversity, composition, and dominance. Systematic random sampling was applied whereby a total of 36 plots of 2500 m2 were set in the seven (7) transects at an interval of 400 m.  Woody plant species were identified for their botanical nomenclature, determined for their abundance. GPS was applied to locate plots, aligning transects and recording coordinates for plot site and map production. 100 m tape was used to set the plots. H' and ID were applied for species diversity and dominance. A total of 129 woody plant species were identified belonging to 38 families and 89 genera. The H' ranged from 0.1831 ± 0.0021, with an overall total of 4.271 while ID ranged from 0.004657 ± 0.000015 with a total of 0.02079 an implication of high wood plant diversity, as the higher the H', and the lower the ID the higher the diversity.  MGBFR consists of high woody plant species diversity. Further study should be done to assess all plant forms of MGBFR, education provision to community, establishment of ecotourism industry to sustain the forest reserve.