This study aimed to assess Maasai pastoralists’ perception and attitude towards the spread and impacts of sickle bush (Dichrostachys cinerea) in their grazing lands. The study was conducted in three villages of Monduli district involving 156 randomly sampled households. Thirteen (13) purposively selected key informants (based on their merits) were interviewed and participant observation was also used in data collection. Quantitative data were analyzed by the SPSS software version 20, while qualitative ones were subjected to content analysis. Findings revealed that the current extent of the sickle bush has increased, with over 70% of the respondents proving this. About 82% of respondents revealed that the bush was present in their villages for a long time, although its invading effects have increased. Major reasons for this invasion were reported to include climate change and overgrazing. Furthermore, sickle bush was reported to take over the grazing lands. The bush is perceived as destructive by the Maasai community because it depletes the amount of forage for livestock grazing. It also provides suitable habitats for predators such as lions and enhances conflicts with livestock and humans.