Three-dimensional (3D) bioprinting has revolutionised the field of biofabricationby delivering precise, cost-effective and a relatively simple way of engineering in vitro living systems in high volume for use in tissue regeneration, biological modelling, drug testing and cell-based diagnostics. The complexity of modern bioprinted systems requires quality control assessment to ensure the resulting product meets the desired criteria of structural design, micromechanical performance and long-term durability. Brillouin microscopy could be an excellent solution for micromechanical assessment of the bioprinted models during or post-fabrication since this technology is non-destructive, label-free and is capable of microscale 3D imaging. In this work, we demonstrate the application of Brillouin microscopy to 3D imaging of hydrogel microstructures created through drop-on-demand bioprinting. In addition, we show that this technology can resolve variations between mechanical properties of the gels with slightly different polymer fractions. This work confirms that Brillouin microscopy can be seen as a characterisation technology complementary to bioprinting, and in the future can be combined within the printer design to achieve simultaneous real-time fabrication and micromechanical characterisation of in vitro biological systems.