A dual-band slotted waveguide array (SWA) antenna is designed using a single waveguide by placing the radiating slots for 18 GHz and 24 GHz on the same antenna aperture. These bands are excited using a single excitation point through a conventional waveguide feeding technique to radiate unidirectional radiation patterns of same polarization. Theoretical analyses are carried out to study the conductance of the slots to understand their effects on the dual-band performance. Numerical analyses are performed to optimize the antenna by considering mutual coupling. The antenna is fabricated using stereolithography (SLA) and direct metal laser sintering (DMLS) processes to compare its performance in different additive manufacturing techniques. In characterizing the fabricated prototype, an impedance matching of | S 11 | < −10 dB and the boresight antenna gains of 14 dBi and 17.4 dBi are measured in these bands with unidirectional and linearly polarized radiation patterns. A quantitative comparison among dual-band SWA antennas is presented at the end of the manuscript to highlight the uniqueness of the proposed approach over the state-of-the-art solutions.