The aim of this research was to examine the feasibility of producing fully ceramic composites (that do not contain metal phases) via binder jetting of alumina preforms, followed by spontaneous infiltration with copper in air. Alumina powders with varying particle sizes (submicron and micron) were utilized for binder jetting. Post-processing steps, including curing, depowdering, debinding, and sintering, were subsequently applied to the sintered samples. Both powders yielded sintered samples with high porosity and low mechanical properties. However, the infiltrated samples of both powders attained nearly full density, with substantially enhanced mechanical properties. The compressive strength of 826.0 MPa and the flexural strength of 317.5 MPa obtained in this study exceeded those of any previously reported alumina-based samples created using binder jetting followed by sintering and/or infiltration.