ABSTRACT Homegarden agroforestry is one of the common practices in the Central part of Ethiopia. This is because of the multifunctional ecosystem services, such as food, feed, biodiversity conservation and carbon storage potential. This, in turn is useful for climate change mitigation and adaptation under the current changing environment. But structure, diversity and carbon stock status of homegarden (HG) were not well-studied. This study was carried out to assess the influence of land size on floristic diversity, richness, biomass carbon stock and soil organic carbon (SOC). A total of 30 HGs were surveyed in Ephratana gidm using a stratified random sampling. The homegardens were classified into small (<0.06 ha), medium (0.06–0.1 ha) and large (>0.1 ha). The main parameters were landholding size, species names, floristic composition, height, and diameter at breast height (DBH) of all trees and shrubs (>2.5 cm DBH). Biomass of the HG was computed using allometric equations. Statistical analysis was used to choose the suitable allometric equations among developed for tropical regions. The carbon stock was estimated using a constant 47% of biomass. SOC of the homegarden was estimated at (0-60 cm)). A total of 39 woody species, belonging to 24 families were recorded in all the study HGs. Shannon diversity index (H’) was 1.8, 1.6 and 1.9 for small, medium, and large homegardens, respectively. Tree density (625.8 tree ha-1) and basal area (17.3 m2 ha-1) were highest for small-sized holdings. However, large homegardens had more species richness (Margalef Index) per garden (12.4) compared to medium and small size HG. Mean biomass C ranged from 9 to 89.3 ton ha-1. Mean biomass carbon stock per unit area was higher in small HG (49.3 ton ha-1) compared to medium (38.4 ton ha-1) and large (35 ton ha-1). Total C stock (biomass C + soil C, 0–60 cm depth) range from 77.2 to 258.3 ton C ha-1 with a mean value (164.0 ton C ha-1), indicating that a major portion of the total amount of C in the system is stored in the soil. This result implies that homegarden can serve as both for carbon sequestration and conservation of woody species diversity. However, a specific homegarden management plan is necessary to improve the carbon storage and species diversification to the respective area. The results provide a catalyst the implication of the future potential of HG management in carbon storage thereby for climate change adaptation and mitigation purpose. This helps to start the integration of the Reducing Emissions from Deforestation and Forest Degradation (REDD+) concept as a national program. Keywords: Agroforestry; Biomass; Carbon stock; Climate Change; Homegardens; Species Diversity