But looming large over his future is a man not far away, at Trump Tower in Manhattan, who also starts his new job soon.
President-elect Donald Trump has criticized the UN for its failure to perform and for a Security Council vote against Israel on settlements. He even tweeted that the UN was just a place "to talk and have a good time."
When asked if Trump's criticism worried him, Guterres responded, "No. I am concerned about all the terrible problems we face in the world, all the wars that are happening everywhere." He added, "I hope we will all be able to come together."
Guterres, in a Snapchat interview Tuesday, took note of that remark.
"That's exactly what I feel. My job is to make sure that potential becomes a reality," he said.
"The US is a country totally committed to UN reforms and will be an important ally in the work ahead that needs to be done."
The United States is by far the largest funder of the 193 member countries of the UN, providing more than 20% of the UN budget. Any secretary-general has to make sure relations are good with the White House.
This is only the second time a UN secretary-general and a US president will begin their terms within weeks of each other.
Guterres, a former prime minister of Portugal, has been praised by former colleagues for his negotiating skills. He served 10 years as the head of the UN's refugee agency based in Geneva.
UN spokesman Stephane Dujarric said the new secretary-general wants 2017 to be a year of peace, spurred by a surge in diplomacy.
Guterres is a realist.
"We are facing very challenging times," he said in off-the-cuff remarks to dozens of staff members gathered in the lobby, citing global terrorism and refugees as two of the major problems in the world.
The secretary-general noted there's a lot of resentment and skepticism about the UN's role. He told staff members to be proud of their achievements but added that "we should recognize our shortcomings and failures."
Guterres appears to be more to-the-point than his predecessor, Ban Ki-moon of South Korea, and more relaxed. Guterres, for example, spoke without notes to the UN staff.
Guterres concluded by telling the staff, "It's not enough to do the right thing. We need to earn the right to do the right thing."