<p>Agroforestry is highly valued for its role in carbon sequestration and biodiversity enhancement, yet empirical knowledge on how tree diversity and carbon stocks relate to environmental, farm-level, and household factors remain limited. This study combined whole-farm tree inventories and household surveys across 55 farms in Laikipia East Sub-County to assess patterns and drivers of woody species diversity and aboveground carbon stocks. A total of 108 woody species (6,756 individuals) across 38 families were recorded. Native species accounted for 56% of all species but only 40% of individuals, indicating dominance by a few exotic species. Species richness was highest in croplands (70 species) and boundary areas (59 species), which together accounted for 65% of all recorded trees. Young trees dominated the farms (&gt;50%), mature trees made up about one-third, while large trees (&lt;10%) were mostly confined to boundaries and croplands. Aboveground carbon stocks varied widely (mean:&#xa0;16.5±7.1&#xa0;t&#xa0;C/ha), with highest densities in woodlots (40.0±12.7 t C/ha) and homegardens (20.0±9.5 t C/ha). Multivariate analyses showed that plant density and average tree size were the strongest predictors of aboveground carbon (p&lt; 0.01), while species richness was influenced primarily by the diversity of agroforestry practices and selected household characteristics, including respondent’s gender and household size (<i>p</i> &lt; 0.05). Species diversity showed a weak relationship with aboveground carbon stocks (r &lt; 0.20). These findings highlight both the ecological value and structural limitations of smallholder agroforestry. We recommend promoting tree conservation, native regeneration, and diversified agroforestry practices as strategies to enhance carbon storage and biodiversity outcomes in the region.</p>