An experiment was conducted to determine the effect of egg size on hatchability of Guinea fowl keets. Three different egg size groups (treatments): small (<39 g); medium (39 - 42 g) and large (>42 g)] were used in the experiment. Each treatment had three replicates of 10 eggs each. A complete randomized design was used for the experiment. Eggs were incubated with their sharp ends pointing downwards at 37.5 - 37.8oC and 60% relative humidity for 28 days. Thereafter, incubation parameters including hatchability (number of eggs that successfully hatched), dead in shells (DIS), clears, pips and keets with deformities evaluated. Data were analyzed using General Linear Model (GLM) of SAS. Medium sized eggs had significantly (P<0.05) higher hatchability than small eggs. Also, medium sized eggs had lower pips. Egg size did not have effect on DIS, clears and deformities. The results of the present study showed that medium sized eggs (39 - 42 g) hatched best in comparison to both small and large categories. Keywords: Dead in shells, deformities, egg size, guinea fowl, hatchability, incubation