Guterres, who served as UN refugee chief for 10 years, received 11 votes of encouragement, three "discourage" votes and one "no opinion" during the informal vote held yesterday by the 15-member Security Council.
It is the third time that the 67-year-old has taken the number one spot in the contest to succeed Ban Ki-moon, who steps down on December 31 after 10 years as the world's top diplomat.
During the first round, Guterres took the lead with 12 "encourage" votes and three "no opinion," but he picked up two "discourage" votes in the second straw poll, along with 11 encouragements and two "no opinion."
"He remains well ahead of the pack," a Security Council diplomat said, speaking on condition of anonymity.
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Slovak Foreign Minister Miroslav Lajcak made a surprise showing as the runner-up, climbing up the rankings with nine encouragements, five discourage votes and one "no opinion."
He took the sixth position in the last round.
UNESCO chief Irina Bokova of Bulgaria and Serbia's ex-foreign minister Vuk Jeremic tied for the third spot, with seven encouragements and five "discourage" votes, plus three "no opinion."
Lower down the rankings, New Zealand's ex-prime minister and current UN Development Program chief Helen Clark took the number six spot, just below Macedonia's ex-foreign minister Srgjan Kerim.
Clark picked up six encouragements, eight "discourage" votes and one "no opinion," compared to six encouragements, seven "discourage" votes and two "no opinion" for Kerim.
Slovenia's former president Danilo Turk, who had made a strong showing as the runnerup in the first round, dropped to number eight.