Ultrasonic welding is a promising joining technique for thermoplastic composite parts. On the way towards upscaling and industrialisation of this technology, it is crucial to understanding how it is affected by manufacturing tolerances. The objective of the research presented in this paper was to investigate the influence that misaligned adherends have on static ultrasonic welding of thermoplastic composites. Different angles were created by changing the clamping configuration. The results showed that increasing the angle between adherends decreases the power consumed and increases the process time while decreasing the weld uniformity and increasing the risk of overheating. These effects were associated to the impact of the different clamping configurations on the cyclic strain in the energy director and adherends during the welding process. Decreasing the top adherends bending stiffness by increasing the clamping distance was found to significantly reduce the adverse effects of adherend misalignment on weld quality.