To leverage the unprecedented design freedom of additive manufacturing (AM), this work aims to develop a design methodology for lattice structures fabricated by rapid investment casting (RIC). What lattice topological properties have the most significant impact on the overall performance in RIC, and how to improve them? The hypothesis is that the relative strut size, number of joints, joint valence, and strut angle significantly affect the performance. There is no overarching analysis of the effect that lattice topology has on casting performance. To remedy this, various lattice topologies underwent mold flow simulation, finite element analysis, casting experiments, and grain structure analysis. From the results, a set of design guidelines for RIC is created, and new lattice structures are designed. The design recommendations by importance are as follows. A relative strut size, number of joints, and joint valence should be below 0.20, 9, and 8, respectively. For mechanical performance, the strut angle distribution should include vertical, diagonal, and horizontal struts. The two proposed topologies:​ proposed cell and hourglass, meet all these criteria and achieve good casting and mechanical performance.