An outstanding junior, Ellwood won the boys' singles at the 1994 Australian Open, defeating Andrew Ilie in the final.

As a doubles player he had much more success, with his best result being a quarter-finals berth at the 1999 US Open, with Michael Tebbutt as his partner.

He also competed in the mixed doubles and made the second round of two Grand Slams in 2002, at the Australian Open and Wimbledon, both times with Evie Dominikovic.

These would be the only two occasions he won a Grand Slam mixed doubles match but he only twice played with his younger sister, Annabel Ellwood, in the 1998 Australian Open and 1999 Wimbledon Championships.

[1] On the ATP Tour, Ellwood made his only final when he and David Adams were doubles runners-up in the 2002 Delray Beach International Tennis Championships.