Lamellar graphite iron (LGI) is used in the automotive industry as well as in a variety of other industries for geometrically complex components with demands on good balance between mechanical and thermal properties. Carbon content and cooling conditions influence the fraction and coarseness of the primary and eutectic microstructure that defines the mechanical and thermal properties. A wide range of carbon contents and cooling rates utilized in this work to produce LGI with ultimate tensile strength (UTS) that ranges from 200 to 350 MPa and thermal conductivity (lambda) from 31 to 63 W/m(-1)k(-1). The microstructure was extensively studied, and the results show that UTS and lambda are highly correlated with many different microstructural features. A relationship between the primary dendrites/eutectic interfacial area and maximum eutectic cell diameter is found, indicating the dependency of the eutectic cells diameter on the morphology of the pre-existing primary dendrites.