Livestock herders’ perception on the invasion and effects of Senna obtusifolia L. were gotten from two locations (Kafta Humera and Tsegede) in Northern Ethiopia. From each location, three peasant associations were selected using key formants and group discussion. The invasion level of S. obtusifolia L. was higher near settlements and road side of continuously grazed lands of the study area. S. obtusifolia L. invasion is negatively affecting the grazing lands of the study area. Highly palatable grasses and herbaceous legume species were identified to be increasingly rarer from S. obtusifolia L invade grazing lands. Although unpalatable, herbaceous species was increased in invaded sites in the study area. The replacement of highly palatable grasses and legume species by less palatable and unpalatable herbaceous species in S. obtusifolia L infested grazing lands. This resulted in the shortage of quality and quantity forage for grazing animals near settlements leading to long distance travelling to search for animal feed, and subsequently with the reduction of livestock productivity. Although, S. obtusifolia invasion negatively affect the herbaceous vegetation and livestock productivity with no measure taken into place to control its invasion. Therefore, the collaboration of all stakeholders is needed to optimize the negative impacts of S. obtusifolia invasion.
Key words: Grazing lands, group discussion, invasive species, key informants, palatable herbaceous species.