Sands, who takes up his role in May, will preside over the above-the-line marketing function, public relations, direct marketing, and digital operations.
The remit includes control of the gallery owner's relationship with creative incumbent agency Fallon and digital agency Dewynters.
Sands left GNM at the end of last year after a strategic review of the business, which made his role as marketing director of The Guardian and The Observer redundant.
Tate, owner of galleries including Tate Britain and Tate Modern, is looking to ramp up its digital presence and capture new audiences.
Tate Online had millions of visitors to its website last year. In his new role, Sand will report to the Tate's deputy director, Alex Beard.
Sands, who left GNM after nine years, was also a former marketing director for the ITV venture ONdigital.