As wireless technology advances toward the sixth generation (6G) communication systems, ambient backscatter communication (AmBC) has emerged as a key enabler for low-cost internet of things (IoT) networks. This paper introduces a novel joint localization and communication (JLAC) technique based on orthogonal time sequency multiplexing (OTSM), specifically designed for passive backscatter devices (BDs). The proposed design enhances spectral efficiency by supporting broadband direct link communication, reduces synchronization requirements by leveraging the spreading characteristics of OTSM carriers, and ensures reliable BC even in the presence of strong direct link interference (DLI) without the need for successive interference cancellation (SIC). The approach utilizes pilot carriers that are protected by a guard in the delay-sequency (DS) domain to achieve diversity gains along the delay domain while ensuring zero interference from either the data or the direct link. The scheme also exploits the pilot signal for localization, using received signal strength (RSSI) from BDs to localize the transmitter. Furthermore, the scheme minimizes the energy consumption at the BDs by reducing the switching rate (SR) by a factor ofM. Extensive analysis and simulations demonstrate the proposed OTSM-based JLAC system’s robustness to DLI, synchronization mismatches, power efficiency, and low complexity characteristics.