The left-back, 29 on Sunday was released by Queens Park Rangers at the end of last season after three years at Loftus Road and becomes Gary Megson's fifth signing of the summer.
Padula told the official club website: "I first knew about the possibility of joining Forest last Thursday and I was keen to get the transfer sorted out as soon as possible.
"I'm aware that Forest attract big crowds and I am really looking forward to playing in front of them in a few weeks time."