The 1978 New South Wales Open, also known by its sponsored name Marlboro New South Wales Open, was a combined men's and women's tennis tournament played on outdoor grass courts at the White City Stadium in Sydney, Australia.

The men's event was part of the 1978 Colgate-Palmolive Grand Prix circuit while the women's event was art of the 1979 Colgate Series.

[3] It was the 86th edition of the event and was held from 18 December through 24 December 1978.

The singles titles were won by unseeded Tim Wilkison and second-seeded Dianne Fromholtz.

[4][5] Tim Wilkison defeated Kim Warwick 6–3, 6–3, 6–7, 3–6, 6–2 Dianne Fromholtz defeated Wendy Turnbull 6–2, 7–5 Hank Pfister / Sherwood Stewart defeated Syd Ball / Bob Carmichael 6–4, 6–4 Lesley Hunt / Sharon Walsh defeated Ilana Kloss / Marise Kruger 6–2, 6–1