The 30-year-old has scored 18 league goals in 17 appearances this season for Auckland, who are top of the standings in New Zealand.
Tade, who is in his second spell at the club after a short spell to Club Atletico in 2015 in his homeland, has won the OFC Champions League five times and the league with them in 2013/14.
Another player who is set to join AmaZulu on a pre-contract is Nhlanhla Vilakazi from Free State Stars. The former Ajax Cape Town and Maritzburg United midfielder’s contract with Ea Lia Koto comes to an end in June.
A few weeks ago, AmaZulu general manager Lunga Sokhela tweeted on his Twitter account, saying: "just made a good signing on a pre-contract. All will be revealed in good time."
Usuthu coach Cavin Johnson claims he knows nothing about the signing of Tade.
“Emiliano? From New Zealand? I don’t know about it,” Johnson laughed during today's media day.
“But everybody is always looking for strikers, everybody is always looking for good goalkeepers, everybody is always looking for defenders, but we are not immune to looking elsewhere for players.”
On signing Vilakazi, Johnson again sarcastically responded: “Midfielder? He’s coming and he’s coming.”
With Tade coming in, the future of former Kaizer Chiefs striker Camaldine Abraw is in doubt, after he was signed in January on a deal until the end of the season.
Abraw has only featured five times in all competitions, with no goals.