Caulerpa filiformis is a green alga considered native to both South Africa and the east coast of Australia but invasive in Peru. In Australia, C. filiformis was previously believed to be a subdominant member of shallow rocky shore algal communities with a narrow distribution of approximately 250 km from Jervis Bay to Port Stephens. Unusually, C. filiformis has spread rapidly north and now occurs over 800 km of coastline, extending its range to Hastings Point and potentially Kingscliff. It is now a dominant alga at many sites at which it occurs. We present a synthesis of approximately 10 yrs of studies describing its distribution and abundance across multiple spatial scales - from metres to regional scales. We also review key processes (e.g. macroalgal loss, sedimentation and colonisation by turfing algae) operating across the same spatial scales that may have contributed to its spread and increased local abundance. Finally, we consider the potential consequences of the increased local abundance of C. filiformis for shallow subtidal faunal communities– particularly its influence on the abundance and life history of key herbivores.