Currently, no publicly available comprehensive set of specifications exists for the design of ground‐penetrating radar antennas. Specifications are presented and derived for the design of a ground‐penetrating radar antenna based on the antenna's interaction with the rest of the radar system. Typically, ground‐penetrating radar antenna engineers are given basic parameters such as gain and bandwidth to design an antenna. An antenna can be designed to meet those specifications but may not perform well in a ground‐penetrating radar imaging system. By considering the whole system, including the operation parameters, expected targets, and signal processing algorithms, we can constrain the less‐commonly considered performance aspects of an antenna to perform more reliably in a deployment. We propose quantitative specifications for the antenna's coupling, beamwidth, boresight radar cross‐section, pulse integrity, residual ringing, and front‐to‐back ratio. Meeting these antenna specifications will decrease the probability that a deficiency in the antenna design impacts the radar's image output. Finally, a summarised design equation table that will be helpful in the ground‐penetrating radar antenna community at large is offered.