Tidal energy converters (TEC), e.g., marine hydrokinetic turbines, harness the kinetic energy of tidal currents to generate clean renewable power. The overarching goal of this project is to design, build, and deploy an instrumented marine turbine system in a real tidal environment. The Open-Source Tidal Energy Converter (OSTEC) will serve as a testbed for research and development (R&D). With its 2.5-meter diameter rotor plane, this tidal turbine will generate open-source datasets on power performance, mechanical and design loads, and tidal inflow conditions at meaningful Reynolds number scales. This contribution will focus on integrating the OSTEC system, comprised of two main subsystems shown in Figure 1: a) a three-bladed axial flow hydrokinetic turbine for power generation, b) a sensor-instrumentation and data acquisition (DAQ) system for measuring inflow conditions, power performance, and mechanical loads on turbine components. System integration combines different assemblies, sub-assemblies, and components of a system into one cohesive whole. For the OSTEC instrumented turbine, the goal is to coordinate the testing, connection, and assembly of individual components, sub-assemblies, and the full system in an organized way to verify and ensure they function as specified on the component, sub-assembly, and system level, and to ensure they work seamlessly together to enable the system to achieve specified design basis functionalities and design objectives. The flow chart in Figure 2 illustrates the sequence and interdependencies of testing, assembly, and system integration planned for the OSTEC turbine at the Atlantic Marine Energy Center, University of New Hampshire, in collaboration with partners Sandia National Laboratories, National Renewable Energy Laboratory, and Pacific Northwest National Laboratory. Several parallel tasks will be conducted during the turbine system integration. PTO control and instrumentation will be integrated into a UNH-built variant of the NREL Modular Ocean Data Acquisition (MODAQ) system. MODAQ will also serve as the primary health monitoring system for the turbine on monitoring sensor faults, overload conditions, etc., as well as turbine control setpoint. To synchronize clocks throughout the DAQ network, a precision time protocol (PTP) scheme is utilized. Additionally, a custom-built test and assembly stand streamlines the integration process. The turbine system will be equipped with dozens of sensors and instruments and generate large data volumes during deployment. The instruments will be accurately tested and integrated during the system integration process. Once the assembly process and system integration on a test stand is completed, the turbine will undergo a dry test, rotating via a motor to check mechanical integrity and ensure proper functioning of all components and instruments. Then, the system will undergo a leak test and then be prepared for deployment at the UNH Pier Facilities. Meanwhile, The Turbine Deployment Platform will be relocated to the UNH Pier for modifications and installation of OSTEC. In summary, the turbine system integration aims to optimize system integrity, reliability, efficiency, operation, and lifecycle by seamlessly integrating various components, controls, and infrastructure. It requires multidisciplinary expertise in mechanical engineering, electrical engineering, control systems, and project management. This contribution will provide updates on the system integration of the OSTEC Testbed.