Booker defeated Republican opponent Steve Lonegan and will replace interim Sen. Jeffrey Chiesa (R-N.J.), giving Democrats back a seat in the Senate; they now have a total of 55.

Reid touted Booker’s hard work as mayor during Hurricane Sandy and said he would add deep knowledge on issues such as climate change and economic development.

It's unclear when Booker will be sworn in as a member of the Senate, which returns to work Oct. 28.