Groundwater depletion is an increasing livelihood concern in Kisasi Sub-County, Kitui County, Kenya, where households depend on boreholes and shallow groundwater for domestic use, farming, and livestock. This study evaluated the perceived magnitude of groundwater depletion, the key environmental and human factors contributing to it, and its socio-economic consequences for households. A descriptive survey design using a structured household questionnaire was used. Data were collected from 368 adult household respondents in Mosa, Masimbini and Maliku. Quantitative data were analysed using frequencies and percentages, while Pearson correlation and multiple regression examined the association between selected environmental and human factors and a household-reported depletion index. The reported magnitude of depletion was substantial: 79.3% of respondents reported declining groundwater availability over the preceding five to ten years, 74.5% reported drying shallow wells or seasonal springs, and 71.2% reported reduced borehole yields. Climate change and poor rainfall was the most widely reported driver (81.5%) and showed the strongest correlation with depletion (r = 0.802, p < 0.001), followed by excessive borehole drilling (r = 0.793, p < 0.001) and deforestation (r = 0.762, p < 0.001). A multiple regression model with five reported drivers explained 78.3% of the variance in the depletion index (R = 0.885, R² = 0.783, F(5, 362) = 261.45, p < 0.001). Livelihood effects included reduced crop production (73.4%), increased water costs (69.8%), livestock losses (65.2%), health problems (61.4%), community conflict (58.7%), school absenteeism (54.3%), and worsened poverty (71.2%). The study concludes that groundwater depletion in Kisasi is a combined climatic, governance, and land-management problem with wide-ranging livelihood consequences, and recommends coordinated borehole regulation and monitoring, land and recharge protection, and livelihood-support interventions.