It said the broadcaster had posted material that contradicted expert advice about the coronavirus pandemic.
But it explained its U-turn saying it sometimes made exceptions to guidelines that state repeat offenders face a permanent ban.
TalkRadio said it had yet to be given a full explanation for the affair.
The decision to ban TalkRadio had appalled digital rights campaigners, with one group - Big Brother Watch - claiming it was evidence that "big tech censorship is spiralling out of control".
The Google-owned service has issued a brief statement explaining its actions.
"TalkRadio's YouTube channel was briefly suspended, but upon further review, has now been reinstated," it said.
"We quickly remove flagged content that violates our community guidelines, including Covid-19 content that explicitly contradict expert consensus from local health authorities or the World Health Organization. We make exceptions for material posted with an educational, documentary, scientific or artistic purpose, as was deemed in this case."
YouTube has not published details of the offending posts.
But independent fact-checkers have repeatedly challenged some of the claims made by interviewees featured by the London-based radio station.
YouTube operates a "three strikes" policy, whereby channels that break its community guidelines three times within a 90-day period can be permanently banned, but other infractions lead to temporary restrictions.
Prohibited content includes "medically unsubstantiated claims" relating to Covid-19, and videos that contradict expert consensus from local health authorities such as the NHS.
"YouTube is making decisions about which opinions the public are allowed to hear, even when they are sourced to responsible and regulated new providers," TalkRadio said in a statement this evening.
"This sets a dangerous precedent and is censorship of free speech and legitimate national debate."
The broadcaster tweeted the statement minutes after YouTube's change of heart. It did not appear to be aware that its channel had been reinstated at the time, but has since acknowledged the move.