Anthony Scaramucci, a hedge-fund investor who is representing the Trump team at the World Economic Forum in Davos, said the next US president was a "man of peace" who "recognizes the importance of the long-term alliances that we've got with Europe".
But he acknowledged that Trump is also seeking to build bridges with Russian President Vladimir Putin, moving on from hostilities over the war in Syria, Ukraine and allegations of state-sponsored cyber attacks.
"He wants to have a great relationship with Angela Merkel as he does with President Putin," Scaramucci told reporters in the Swiss resort of Davos, where 3,000 members of the political and business elite are gathered for annual talks.
"I don't see him as somebody who wants to have a bad relationship with people and he certainly doesn't view Europe as weak.
"In the next six months, in the next year, the relationship between the United States and Europe will be stronger than ever," Scaramucci said.
But he added: "I think he said something that you guys should listen to - that we have to make sure that our structures, our alliances or charters are in preparation for the 21st and 22nd century, not the 20th century."
Trump unleashed a volley of attacks on Europe in a hard-hitting interview with two European newspapers on Sunday, branding NATO "obsolete" and saying more countries would leave the European Union after Britain.
The Republican billionaire, who takes office Friday, also criticized Merkel's "catastrophic" decision to open Germany's borders to hundreds of thousands of refugees and immigrants.
Despite a backlash in Europe over the comments, Scaramucci said the interview reflected Trump's "authenticity", adding: "You should find this refreshing and not alarming. He is open with his views."