Invasive alien plant species are one of the major drivers of global ecosystem change and the most serious threats to ecological, economic and social well-being. Their current spread is damaging livelihoods in rural areas by increasing poverty while simultaneously affecting biological diversity. Like many other countries, Kenya is faced with the problem of increased occurrence of invasive alien plant species. One of the species that is spreading rapidly and threatening rangelands is Opuntia engelmannii Salm-Dyck ex. Engl. (cactus apple), which reduces rangeland access and productivity by forming dense impermeable thickets, therefore contributing to increased pressure on the diminishing pasture resources. This consequently threatens pastoralists and agro pastoralists who are the main inhabitants of these lands. This study will therefore assess the socio-economic impacts of O. engelmannii to local livelihoods and their environment with a special focus on (i) the local communities’ perceptions on the impacts and benefits, (ii) impacts on production, access and availability of forage in grazing areas and (iii) displacement of indigenous vegetation cover. The study will encompass literature review, socio-economic survey and field work in order to provide holistic information that will be useful in ecosystem management, biodiversity conservation and improvement of human well-being.