"My daughter Ivanka has been treated so unfairly by Nordstrom," Trump said in a tweet. "She is a great person -- always pushing me to do the right thing! Terrible!"
The retailer, which has about 350 stores in the United States and Canada, said last week it was dropping Ivanka Trump's line -- which includes high-end women's clothing, accessories and shoes -- due to poor sales.
Since his surprise victory in the November presidential election, Trump has used his Twitter feed to lambast companies for off-shoring jobs or for allegedly overcharging the federal government for aircraft.
But the latest tweet was different in that it sought to defend part of Trump's family business empire, which critics have said could be a source of profound conflicts of interest for the White House.
Unlike other companies he has attacked on Twitter, including Lockheed, Boeing and Ford, Nordstrom stock had gained nearly one percent in the early afternoon.
The upscale retailer did not immediately respond to a request for comment from AFP about the Twitter attack, but Nordstrom said in a statement last week that its decision was based purely on commercial merit.
"In this case, based on the brand's performance, we've decided not to buy it for this season," the company said, noting the phase-out was part of its regular review of the 2,000 brands it sells.
Nordstrom was one of several retailers that faced boycott calls for selling Trump family products or supporting the campaign.
Anti-Trump activists created "Grab Your Wallet" after the election to enlist consumers in boycotts to protest Trump's agenda, which also has been met by waves of demonstrations inside and outside the United States.
