Yousaf swore allegiance to King Charles III, Prime Minister of the Scottish Autonomous Administration, at a ceremony held at the High Court.
It is the first time that a Muslim politician assumes such a high-level position in the United Kingdom, which consists of England, Scotland, Wales and Northern Ireland.
Yousaf, the son of South Asian immigrant parents, said in his speech before the vote, "It is my greatest privilege to be here as a candidate for Prime Minister of Scotland."
"Scotland's best days are near," said Yousaf.
Humza Yousaf shared a photo of himself on Twitter while leading the tarawih prayer with his family on his first night at the Prime Minister's residence, Bute House.
SNP leader Nicola Sturgeon announced last month that she will be leaving the party leadership for more than eight years, and Humza Yousaf, 37, was elected leader yesterday, winning 52 percent of party members in the runoff.
Who Is Humza Yousaf?
Former Scottish Health Minister Humza Yousaf has also served as Minister of Justice and Minister of Transport in the self-government since 2012.
Humza Yousaf's father is of Pakistani descent and immigrated to Scotland in the 1960s. His mother was born in Kenya to a South Asian family.
Yousaf also said that he had often encountered racism in the past.
Yousaf said it would be "the greatest privilege and honor of my life" to serve as Prime Minister of Scotland. "This is beyond my family's wildest dreams," he said.
Source: BBC