"I'm not supporting anybody right now," Webb told MSNBC's "Morning Joe" on Friday morning.
"No, I would not vote for Hillary Clinton," he added.
Webb said he wasn't sure whom he'd support for president and said his issue with Clinton was "nothing personal." He also said he hasn't ruled out Trump.
"A certain group of people are seeing him as the only one who has the courage to step forward and say, 'We've got to clear out the stables of the American governmental system right now,'" Webb said.
He suggested a Trump presidency could be either highly positive or highly negative, while Clinton represented a continuation of the political norm.
"If you're voting for Donald Trump, you may get something very good or very bad. If you're voting for Hillary Clinton, you're going to be getting the same thing," Webb said.
Webb served in former President Ronald Reagan's administration as secretary of the Navy and assistant secretary of Defense. He served as a Democratic senator from Virginia for one term, ending in 2013.
Webb was a candidate in the Democratic presidential primary but dropped out in mid-October after not gaining traction. He flirted with launching an independent bid but ruled that out