Alien species can be introduced into a new environment intentionally or unintentionally. They may find better conditions than their natural ones and become invasive, affecting the biodiversity and performance of ecosystem services. This work reviewed Botswana’s distribution and control management options for four alien species, Cenchrus biflorus Roxb., Verbesina encelioides (Cav.) Benth. & Hook. f. ex A. Gray, Prosopis juliflora (Swartz) DC, and Salvinia molesta D. Mitch. The discussions on C. biflorus and V. encelioides are based on our published work and from the literature, whereas for S. molesta and Prosopis species are based on the literature and personal observations. Cenchrus biflorus studies in Central Kalahari Game Reserve showed it negatively affected biodiversity and agricultural production. Other studies have revealed an invasion and negative impact of V. encelioides in Botswana, whereas some have identified some adverse effects of Prosopis species. The presence of an alien aquatic free-floating water fern, mochimbamo (S. molesta), was reported in the Okavango Delta. The species hurts the tourism and fishing sectors and biodiversity. This chapter uses these four species to demonstrate the impact of invasion by alien species on ecosystem services and biodiversity. Also discussed are control measures used nationally and internationally.