"Without a doubt it will be a challenge," said Rousseff about his new position. Prior to Tuesday, he was serving as Brazil's energy minister.
Rousseff takes the post left by former Chief of Staff Jose Dirceu who stepped down after he was implicated in a corruption probe.
A federal deputy said Dirceu had firsthand knowledge of a plan to pay off lawmakers for their support in the Congress.
Though Dirceu denied his involvement he stepped down last Thursday.