This study aimed to determine the effect of calcium carbonate (CaCO3) acquired from local marine shellfish on the laying performance of Japanese quail. It was conducted from May to June 2022 at San Nicolas Balas, Concepcion, Tarlac. A total number of 306 Japanese Seattle quail were randomly distributed in an experiment with two-factor (factorial experiment) arranged in Complete Randomized Design (CRD). Factor A indicates the two local marine shellfish Al - Oyster shell meal and A2 - Mussel shell meal. The treatment combinations are as follows: A1B1 ~ 100 % commercial feeds (0% OSM), in AlB2 - 97% commercial feeds + 3% OSM, A1B3 - 95% commercial feeds +5% OSM, in A2B1 - 100% commercial feeds (0% MSM), A2B2 - 97% commercial feeds + 3% MSM, and A2B3 - 95% commercial feeds +5% MSM. There were six treatment combinations and each treatment was replicated three times with 17 birds per replication. The effect of calcium carbonate acquired from local marine shellfish on the laying performance of Japanese quail were noted to improve the egg size from mussel shell meal at 5% level which happen to have an important aspect from the cause of breakage of egg and feed consumption. There were significant differences among treatments but mostly not significant in term of egg produced.