This 5G NR Sidelink Link-Level Simulator (LLS) is developed by National Institute Standards and Technology (NIST) developers by leveraging the MATLAB-based Vienna 5G NR Link Level Simulator. It requires the Vienna 5G NR LLS Release 1.2, licensed by Institute of Telecommunications TU-Wien and available at https://www.tuwien.at/etit/tc/en/vienna-simulators/vienna-5g-simulators/. It also requires MATLAB version 2021b with the following toolboxes: communication toolbox, 5G tool-box, and signal blocks. The Sidelink simulator is released as a patch file to the Vienna 5G LLS v1.2. Once the original Vienna LLS is downloaded, the patch file can be installed using any common patch application method. The section "Installation Guide" in the user manual (5G_sidelink_LLS_userManual.pdf) provides details on two common methods. This software will be actively maintained. Read the LICENSE.md for information on NIST license, and user manual 5G_sidelink_LLS_userManual.pdf on how to use the simulator. Disclaimer: Certain commercial software are identified through the project code and documentation in order to specify the experimental procedure adequately. Such identification is not intended to imply recommendation or endorsement by NIST, nor is it intended to imply that the materials or equipment identified are necessarily the best available for the purpose.