This paper discusses the processes involved in the additive manufacturing of a regenerative and film-cooled liquid rocket engine with a thrust of 10 kN using Inconel 718, while detailing validation techniques. A description of the objectives and design constraints provide the context and motivations. Computational Fluid Dynamics (CFD) models were developed and provided the expected pressure and thermal regimes under regenerative and film cooling. Additionally, Finite Element (FE) models were used to predict the capabilities of the engine structure. A description of 3D printing methods highlights the benefits and limitations of the technology, specifically the influence the design of liquid rocket engines. A pintle injector is used, printed as a separate, easily removable and replaceable component. Issues related to overhangs, surface roughness, and shrinkage; aspects related to post-print processing and the need to minimize machining are discussed. Results from the CT scans of the engine and its components are presented. The paper also outlines the series of tests that will be performed on this engine to verify its performance and provide design basis for future works This engine will be used to power the reusable flight vehicle that is under development at the Kyushu Institute of Technology in Japan. The student-led Liquid Propulsion Laboratory at the University of Southern California is responsible for the work detailed below.