The 37-year-old, who has played 64 times for his country, has penned a one-year deal with the Dragons.
Scottish prop Dave Young, 29, has also joined the club on a two-year contract.
"Recent reports on Welsh regional rugby have been very negative but I see the Dragons as being one of the positives to come out of it," Gough told Newport's official website.
"The squad have come so far under Lyn Jones's guidance this season - it's great to see that sleeping giant has finally been awoken."
Gough joined London Irish on a short-term deal back in September.