An in-situ metal laminate base on ultrahigh carbon steel (UHCS) has been made by the decarburization process where the UHCS plate is exposed to air at elevated temperature. The result is a three-layer laminate which reveals a UHCS layer in the center and decarburized ferrite layers on the outside. The composition of UHCS for this investigation is UHCS-1.8C-6Al. The decarburization temperature, soaking time, cooling rate and post-processes of mechanical rolling and selective heat treatment determine the microstructure of the in-situ laminate. Mechanical properties of the in-situ laminate are dependent on the microstructures in both the decarburized layer and the UHCS layer. Room temperature tensile tests over a wide range of different micro structures (tempered martensite, pearlite and spheroidite) in the central UHCS layer have been studied. The test results revealed that the in-situ laminate has high strength as well as good ductility. The yield strength of the in-situ laminate can be estimated by an isostrain concept based on the yield strength of its constituents. The uniform ductility is shown to be related to Voce strain hardening exponent.