Oocyte-secreted growth differentiation factor-9 (GDF9) plays critical roles in oocyte development by directing differentiation of the cumulus cell lineage from the granulosa cells to provide essential metabolic support for the oocyte. How oocyte-secreted GDF9 effects are restricted to cumulus cells is unknown. Recent reports show that GDF9 effects on cumulus cells can be disrupted with exogenous heparin. Heparan sulfate proteoglycans (HSPGs) are cell-surface glycosaminoglycans with a similar structure to heparin. We hypothesised that endogenous HSPGs sequester GDF9 at cumulus cell surfaces thereby restricting signalling during oocyte maturation. To explore this, we determined the temporal expression of heparan-sulfate (HS) synthesising enzymes during maturation of cumulus oocyte complexes (COCs). We found that Ext1 was significantly induced by 3- and 6.04-fold at 4- and 16-h of in vivo maturation (IVV), respectively, when compared to immature COCs (P<0.05). However, Ext1 was dysregulated during in vitro maturation (IVM) with significantly less Ext1 transcript at 4- and 16-h of maturation compared to IVV. Similarly, Ext2 was significantly reduced in IVM at 8- and 16-h of maturation compared to IVV (P<0.05). This was supported by a significant increase in sulphated glycosaminoglycan (including HS) during IVV with no increase observed during IVM. Lastly, we investigated the role of HS in determining oocyte quality during IVM using heparin and heparin+exogenous-GDF9. Heparin treatment significantly dampened cumulus expansion, which was restored by co-treatment with exogenous GDF9, as previously shown . Interestingly, heparin treatment during IVM impaired oocyte quality with a 1.3-fold reduction in blastocysts following fertilisation, which was restored by exogenous GDF9 co-treatment during IVM. Although not significant with the limited sample size, this data indicates that HS trapping of GDF9 during maturation may be required for oocyte quality. Collectively, the data suggests that HSs play an essential role in GDF9-signalling during oocyte maturation.