To cheers in the National Assembly, Maduro dedicated his oath of office to "the eternal memory of the supreme commander" Chavez, who dominated this oil-rich South American country for 14 years until dying from cancer in March.
But the new leader's speech was briefly disrupted when a man in a red shirt rushed onto the stage and roughly pushed Maduro aside to grab the microphone, a breach that led to national television coverage of the event being suspended.
The intruder was removed from the stage and Maduro returned minutes later, clearly angry at the disruption.
"Security has absolutely failed. They could have shot me here," he said, but shaking it off, then declared: "Incident overcome."
Maduro, 50, said in his address that he wanted to begin his presidency "with a call to all Venezuelan men and women to continue to build a better fatherland of peace, an inclusive fatherland for everyone, by everyone."
He urged the opposition to "converse in the different settings where conversations can be held. I am ready to converse even with the devil."
But he then resumed his attacks on those same foes, highlighting what has been a week of soaring political tensions since he was declared the winner of Sunday's snap elections by a narrow margin of 1.8 percentage points.
Looking on were foreign leaders, MPs and other dignitaries who packed the assembly chamber for the swearing-in.
Close allies Presidents Raul Castro of Cuba and Mahmoud Ahmadinejad of Iran were in the audience, along with the presidents of Brazil, Argentina, Uruguay, Bolivia, Peru, Nicaragua, and neighbouring Colombia.
Maduro had met the night before in Lima with regional leaders who extended their congratulations to the new government and urged all sides in the bitterly contested elections to accept "the official results."
The endorsement came just hours after Venezuelan election authorities announced they would conduct an expanded audit of Sunday's ballot returns in response to opposition demands for a full recount.
Opposition candidate Henrique Capriles immediately accepted, congratulating his followers on their "struggle for the truth."
Violent post-election protests left eight people dead and dozens hurt, igniting a crisis as Maduro and Capriles traded fiery accusations over who was to blame.
For Maduro, the election was the culmination of a political career that took him from one-time bus driver and union organiser to Chavez's handpicked successor.
"I am the first post-Chavez president in history," Maduro said on the eve of his swearing-in. The new first lady, Cilia Flores, is a heavyweight in her own right in the ruling United Socialist Party of Venezuela.
But Maduro also lost the votes of hundreds of thousands of Chavez supporters to Capriles, a 40-year-old state governor who was defeated by the comandante in October by an 11-point margin.
The weak election performance suggested Maduro has yet to step out of Chavez's giant shadow with a mandate of his own.
As Maduro entered the National Assembly, supporters showered him with cheers of "Chavez lives, the struggle continues."
Later at an esplanade dedicated to the country's founders, military leaders pledged their loyalty to Chavez's socialist revolution and their new commander-in-chief.
While backed fiercely by the ruling PSUV and the deep pockets of Venezuela's state oil industry, Maduro must also contend with an emboldened opposition and a sombre economic outlook.
Soaring inflation, a weak currency, shortages of basic necessities, and fiscal constraints are a growing challenge to the costly social programs that were among Chavez's signature achievements.
