Sanchez started her career at Carat before joining Mindshare in 2007. She most recently worked at Naked Communications Sydney.
Reporting to the Goodstuff partner Bobby Din, Sanchez will oversee all of the agency's media buying.
Cross transfers over from the sister Omnicom agency Manning Gottlieb OMD, where she was the digital planning director. She started her career at OMD UK in 2001.
She will also take a senior position at Fifty6, the agency's specialist division serving Virgin Media, and will report to Ben Hayes, a founding partner at Goodstuff, and Paul Gayfer at Fifty6.
Andrew Stephens, the Goodstuff co-founder, said: "Goodstuff is all about good people, so we are delighted to have found two more."