"Amber is a problem solver who works across party lines to get results. She is exactly the type of person I want leading my team for years to come," Baucus said.
Cottle replaces Russ Sullivan, who is leaving the Senate after an 18-year career to return to the private sector and spend more time with the 18 young people whom he has fostered.
"He has been a tremendous asset and will be missed,” Baucus said.
Prior to her work in the Senate, Cottle spent a decade working on trade issues, including in the Office of U.S. Trade Representative.
"The Finance Committee staff is second to none and I am excited to have the opportunity to lead this team of talented and dedicated public servants," Cottle said.
"I look forward to working with Chairman Baucus and assisting in his efforts to reform the tax code, create jobs in Montana and across the country, boost the economy and put America back on track."