The aim of this study was to investigate the effects of time, particle size (PS) and level of calcium supplementation above the requirements toward the end of the laying period on egg production and eggshell quality. A total of 675 Isa-Brown layer hens were distributed in a completely randomized factorial arrangement of 3x3x3, using three sprinkling times (08.00, 12.00, 16.00 hours), PC (mash, granular and large size) and amounts (0 g control, 0.75 g/day/h, 1.50 g/day/h) of marble sprinkling as a calcium source. All hens were fed a commercial layer diet from 55 to 67 weeks of age. Sprinkling of 1.50 g marble reduced (P < 0.05) egg production compared to 0.75 g marble, and feed efficiency (FE) compared to that of 0 and 0.75 g marble. Sprinkling of 0.75 and 1.50 g marble increased (P < 0.01) eggshell weight, shell strength and shell thickness compared to that of 0 g marble. The interaction of sprinkling time-by-PS-by-quantity of marble was significant for egg production (P < 0.05), FE and shell strength (P < 0.01). Results showed that sprinkling of coarse marble powder to complete diet increased shell strength without reduction in egg production and FE.