Fernandez, 58, held back tears as she pledged before Congress and a gathering of foreign dignitaries to honor the constitution and the memory of the late President Nestor Kirchner.
"I swear to God, the country and the blessed saints to carry out the office of the president and to honor ... the Argentine constitution," said Fernandez, who wore a black dress with a wide belt and sleeves of transparent lace — mourning garb of the kind she has used since Kirchner's death in October 2010.
"If I don't, then let God, the country and him take me to task for it," the president added, her voice cracking with emotion as she referred to Kirchner.
After accepting the wooden presidential baton decorated with a gold-and-silver version of Argentina's national shield, Fernandez remarked, "This is not an easy day. ...
The president entered the House of Deputies accompanied by her children, Maximo and Florencia, and received the baton from Florencia.
Fernandez summarized a litany of accomplishments during her first term, including policies that have led to the resumption of trials for former officials accused of rights violations during the country's last military dictatorship, which lasted from 1976 to 1983.
The bulk of her support comes from the working classes, who have received pay and pension increases as well as more public aid under her government.
She's also continued evoking the legacy of her late husband, whose death sparked enormous public sympathy at a time when her presidency had been losing support.
At the same time, Argentina's 40 million people are facing economic uncertainty, and the big question for Fernandez is whether to continue the government spending and price controls that worked so well in her first term.
Cutting public spending to prepare Argentina for a dicier economic climate could bring political harm, so the president is expected to try to strengthen the economy without cutting social programs dear to her base.
Fernandez and outgoing Economy Minister Amado Boudou, who assumed the office of vice president, took their oaths before outgoing Vice President Julio Cobos, who has distanced himself from Fernandez over the past two years.
Foreign dignitaries attending the inauguration included female Brazilian President Dilma Rousseff; the presidents of Bolivia, Chile, Guatemala, Honduras, Paraguay and Uruguay; U.S. Labor Secretary Hilda Solis, and President Barack Obama's senior adviser on Latin America, Daniel Restrepo.
Venezuelan President Hugo Chavez had planned to attend, but canceled at the last minute, citing the need to attend to the needs of citizens in his own country who had been affected by heavy rains that led to flooding and mudslides and claimed the lives of at least eight people.
The 57-year-old president had a cancerous tumor removed from his pelvic region in June and underwent four rounds of chemotherapy. He has said that he is now cancer-free. Venezuelan Foreign Minister Nicolas Maduro attended the inauguration in his place.
