Cross-habitat interactions are essential to maintaining ecosystem function within estuaries. For example, oyster reefs play a key role in connecting the water column to sediments via wave attenuation and benthic-pelagic coupling. However, the effect of oyster reefs on the biodiversity of surrounding sediments remains largely unexplored, particularly for important ecosystem engineers such as bioturbators; which have substantial effects on sediment functioning by oxygenating sediments and boosting nutrient cycling. To assess the relationships between proximity to oyster reefs, bioturbation activity, and sediment oxidation, we surveyed bioturbation activity in sediments surrounding three remnant Saccostrea glomerata oyster reefs in NSW and conducted a reciprocal transplant experiment at remnant reefs in Port Hacking. Our results showed that bioturbation activity and sediment oxygenation was enhanced with increasing proximity to reefs. However, bioturbation activity and sediment oxygenation differed across estuaries implying that these effects vary depending on environmental conditions. Our results suggest that oyster reefs benefit nearby connected habitats through the enhancement of key species that advance critical ecosystem processes. Therefore, oyster reef restoration, a key focus for global restoration efforts, may have positive flow-on effects for nearby systems. However, the ability of reefs to enhance ecosystem function may be dependent on broad environmental settings.