Fetterman waved and said it was "good to be back" before walking in to the building on Monday afternoon.
Fetterman was set to cast his vote to confirm a circuit court judicial nomination on Monday night.
The 53-year-old will also be co-chairing a panel hearing on Wednesday.
The Democrat was treated for six weeks and has previously said that healthcare "changed his life."
SEE ALSO: Pennsylvania Senator John Fetterman speaks out after treatment for depression
Along with the mental health issues, Fetterman has struggled with an auditory processing disorder, a lingering effect of a stroke he suffered last May.
Fetterman now uses devices that transcribe spoken words in real-time.
SEE ALSO: Pennsylvania Senator John Fetterman leaves Walter Reed with depression 'in remission'