"From today, I am Polish. I am one of you," Santos declared at the official ceremony in Warsaw.
"It is an honour to continue my work as a trainer here," he added.
"I am convinced that we will work hard to give the Poles a lot of joy. I am sure that we will achieve success," Santos told journalists at the press conference called to announce the nomination.
Santos, 68, succeeds Czeslaw Michniewicz, who was sacked last month following a last-16 elimination at the World Cup in Qatar.
In one of his first interviews with Polish media, Santos told the Interia news site that his primary focus was on winning.
"Football is not a painting nor... Chopin's music. It is much more simple: if you don't concede goals and you score, then you win. That's all".
Santos said he planned to move to Warsaw and get to know the team.
"I don't want to be the guy that you see only during the matches and on the special occasions," he said.
"I want to get to know the people of Polish football and I want them to get to know me."