In today’s technologically driven world, wireless communication has become ubiquitous, and the demand for faster data rates and the ability to support the ever-growing number of devices is higher than ever. The conventional spectrum is overcrowded, motivating research in utilizing higher frequency bands. As new developments in device and physical layer technologies become more accessible, frequencies above 100 GHz show promise to relieve spectrum congestion and enable new high-bandwidth applications that cannot be supported within the current spectrum. Despite the lack of traditional communication systems at these frequencies until very recently, the spectrum above 100 GHz has already been utilized for passive sensing applications, namely, in Earth-exploration satellite services (EESS) with highly sensitive detectors. In order to coexist with these passive users of the spectrum without harmful interference, spread spectrum techniques are proposed as a method to exploit the large available bandwidth at these frequencies while maintaining high data rates and adding an element of security. In this paper, a direct sequence spread spectrum (DSSS) communication system for THz band frequencies is designed, numerically studied and experimentally tested. Successful generation, transmission, and reception of DSSS signals at 130 GHz coexisting with a narrowband interference is demonstrated. Finally, as a study case, the requirements of a DSSS on-the-ground THz backhaul system are derived to ensure coexistence with THz EESS systems.