The production of extracellular matrix by the cumulus oocyte complex is crucial for oocyte maturation; with deficiencies in matrix production associated with ovulatory dysfunction and poor oocyte quality. Furthermore, the expression of several genes responsible for the production of this matrix are positively correlated with live birth in clinical IVF. Interestingly, in other cell types the viscosity of their extracellular matrix is indicative of viability and function, whether the same holds true for cumulus oocyte matrix is unknown. Here we examined whether the viscosity of the cumulus oocyte matrix is indicative of oocyte quality. To measure viscosity, we employed optical tweezers – a technique that uses tightly focused light to trap micron-sized silica particles (1 µm diameter) in 3D. These particles were optically trapped within isolated cumulus oocyte matrix, with viscosity determined by tracking the trajectory of the particle. We utilised two oocyte maturation conditions – in vivo and in vitro maturation – and confirmed differences in oocyte quality. Specifically, in vitro matured cumulus oocyte complexes yielded significantly fewer blastocyst-stage embryos post-fertilisation when compared to embryos derived from in vivo matured oocytes (~30 % reduction in the number of resultant embryos; n = 5 - 10 independent replicates; P < 0.05). Interestingly, the viscosity of the in vitro matured matrix was significantly lower than that derived from in vivo matured complexes (in vivo: 0.785 ± 0.005 mPa.s vs. in vitro: 0.751 ± 0.002 mPa.s; n = 4 independent replicates, P < 0.001). Our results indicate that higher matrix viscosity is positively associated with oocyte quality. This analysis demonstrates the potential of matrix viscosity measurements as an objective measure of oocyte quality. Additionally, this study is the first to utilize optical tweezers for viscosity measurements in reproductive cell types and highlights its sensitivity in quantifying viscosity within microlitre volumes.