Seasonality of rainfall is a key determinant of pasture availability, herd productivity, and hence pastoral livelihoods. Insufficient rain reduces pasture availability, limiting the ability to support livestock and dependent livelihoods. We assessed the implication of increased rainfall variability on pasture production and pastoral livelihoods in Simanjiro district, Tanzania. Household socioeconomic data were collected through a cross-sectional survey between March and June 2014. Simple random sampling was used to select 297 households. We used the Normalized Difference Vegetation Index (NDVI) based on remote sensing as a proxy for pasture availability to assess vegetation changes in the period 1982 to 2019 (using coarse resolution NDVI data available from 1982 to 2016 and higher spatial resolution data covering 2000–2019). Observed trends were related to data on household perceptions about changing rainfall patterns, pasture availability, and the livelihood implications of these changes. We performed multivariate regressions to predict pasture availability, livestock mortality, food security, and income by climatic shocks and herd management. We found a significant positive association between livestock mortality and extreme climatic events, including drought and flooding. We also found a positive association between household food insecurity and pasture scarcity, and livestock mortality. Our study shows that a higher spatial resolution of imagery combined with household surveys can offer a detailed understanding of the chain of relationships from climate to pasture availability, livestock mortality, and associated livelihoods. We recommend policy interventions that promote pastoralists’ capacity to better manage their activities in the context of climate change.