Leftist Rousseff, 62, comfortably won Brazil's presidential run-off election against her challenger, José Serra, a former mayor of São Paulo and representative of the centrist Brazilian Social Democratic Party(PSDB). Rousseff, who will be sworn in on 1 January, won 56% of the vote, while Serra took 44%.
In her campaign, Rousseff, a close aide of outgoing president Luiz Inácio Lula da Silva, had ridden on his undiminished popularity after two consecutive terms in office.
Speaking before cheering crowds in the capital, Brasilia, Rousseff paid homage to Lula, pledging to extend what she called a "new era of prosperity". She also set out the twin goals of her tenure - eradicating poverty while maintaining Brazil's hard-won economic stability.
"We cannot rest while there are Brazilians who are hungry, while there are families living on the street, while poor children are abandoned to their fate," said Rousseff, quoted by Reuters.
Rousseff's victory has been hailed in Bulgaria. She is the daughter of a Bulgarian immigrant.
For several weeks, the Brazilian elections sparked an unprecedented fervour in Bulgaria. The small European nation took unprecedented pride in the rise of a global leader with a traditional Bulgarian family name.
Speaking to Bulgarian TV channel bTV, Rousseff said the she was well aware of her Bulgarian roots, but had not had the chance to speak the language since her father's death, when she was 15.
Rousseff was born in the Brazilian southwest to a Brazilian mother, Dilma Coimbra Silva, and a Bulgarian father, Pedro Rousseff (born Petar Rusev), who left his home country in 1929 to escape persecution for ties to the Communist Party, according to Dilma Rousseff herself.
However, Bulgarian relatives of Petar Rusev tell a different story. According to them, he fled the country - leaving behind a pregnant wife - due to debt problems. He had a son whom he never met and who recently died.
Whatever his past, Pedro Rousseff, a lawyer by training, did well in business in Brazil, re-married and gave his daughter a middle-class upbringing.
Later, at the age of 17, Dilma Rousseff joined a Marxist movement and reportedly was trained in guerilla tactics. Between 1970 and 1972 she was jailed and reportedly tortured.
Once released, she returned to school and graduated in 1977 with a degree in economics. She was working as secretary of energy in the southern state of Rio Grande do Sul when President Lula Da Silva asked her to take over as energy minister in 2003.
The television announcement caught the eye of Rousseff's relatives in the Bulgarian city of Gabrovo, where they have been following her political career ever since. Gabrovo, in central Bulgaria, has organised a photo exhibition revealing details of the Bulgarian genealogy of Dilma Rousseff.
Now Rousseff's Bulgarian relatives say they hope she will visit Gabrovo as president of one of the world's great nations and "recover her roots".