The swearing-in ceremony took place at State House in Dar es Salaam.
Ms. Suluhu has made history by becoming the first female president in Tanzania.
Under the constitution, Suluhu, 61, will serve the remainder of Magufuli’s second five-year term, which does not expire until 2025.
The oath ceremony will be followed by a high-level meeting of her party’s central committee on Saturday. Analysts say, during the meeting, a new vice president will be picked.
A former office clerk and development worker, Suluhu began her political career in 2000 in her native Zanzibar, a semi-autonomous archipelago, before being elected to the national assembly on mainland Tanzania and assigned a senior ministry.
A ruling party stalwart, she rose through the ranks until being picked by Magufuli as his running mate in his first presidential election campaign in 2015.
The Chama Cha Mapinduzi (CCM) comfortably won and Suluhu made history when sworn-in as the country’s first-ever female vice president.
The pair were re-elected last October in a disputed poll the opposition and independent observers said was marred by irregularities.
She would sometimes represent Magufuli on trips abroad but many outside Tanzania had not heard of Suluhu until she appeared on national television wearing a black headscarf to announce that Magufuli had died at 61 following a short illness.
In a slow and softly spoken address — a stark contrast to the thundering rhetoric favoured by her predecessor — Hassan solemnly declared 14 days of mourning.
Hold your breath
Analysts say Suluhu will face early pressure from powerful Magufuli allies within the party, who dominate intelligence and other critical aspects of government, and would try and steer her decisions and agenda.
“For those who were kind of expecting a breakaway from the Magufuli way of things I would say hold your breath at the moment,” said Thabit Jacob, a researcher at the Roskilde University in Denmark and expert on Tanzania.
“I think she will struggle to build her own base… We shouldn’t expect major changes.”
Her loyalty to Magufuli, nicknamed the “Bulldozer” for his no-nonsense attitude, was called into doubt in 2016.
Her office was forced to issue a statement denying she had resigned as rumours of a rift grew more persistent, and Suluhu hinted at the controversy in a public speech last year.
“When you started working as president, many of us did not understand what you actually wanted. We did not know your direction. But today we all know your ambitions about Tanzania’s development,” she said in front of Magufuli.
Getting things done
Suluhu was born on January 27, 1960, in Zanzibar, a former slaving hub and a trading outpost in the Indian Ocean.
Then still a Muslim sultanate, Zanzibar did not merge formally with mainland Tanzania for another four years.
Her father was a school teacher and her mother a housewife. Suluhu graduated from high school but has said publicly that her finishing results were poor, and she took a clerkship in a government office at 17.
By 1988, after undertaking further study, Hassan had risen the ranks to become a development officer in the Zanzibari government.
She was employed as a project manager for the UN’s World Food Programme (WFP) and later in the 1990s was made executive director of an umbrella body governing non-governmental organisations in Zanzibar.
In 2000, she was nominated by the CCM to a special seat in Zanzibar’s House of Representatives. She then served as a local government minister — first for youth employment, women and children and then for tourism and trade investment.
In 2010, she was elected to the National Assembly on mainland Tanzania. Then-president Jakaya Kikwete appointed her as the Minister of State for Union Affairs.
She holds university qualifications from Tanzania, Britain and the United States. The mother of four has spoken publicly to encourage Tanzanian women and girls to pursue their dreams.
“I may look polite, and do not shout when speaking, but the most important thing is that everyone understands what I say and things get done as I say,” Suluhu said in a speech last year.
Suluhu would be the only other current serving female head of state in Africa alongside Ethiopia’s President Sahle-Work Zewde, whose role is mainly ceremonial.