The 30-year-old back-row forward is in France to sign for the second-division outfit and is expected to begin training with his new side this weekend.
The deal is believed to be until the end of the season when Charvis hopes to he will be able to find a contract back home with one of the Welsh regions.
And Charvis, who won his 64th cap at the World Cup, also insisted his international career remains alive after Wales management gave their blessing to the move.
"I want to continue playing for Wales and I want to be in a situation where I can still be picked," said Charvis.
"Andrew Hore (Wales' conditioning coach) has spoken to Tarbes to make sure everything is ok as far as my fitness goes.
"The standard is pretty good in the French second division. Around six of their clubs probably would have been able to compete in our top flight last year."
Charvis admitted he was disappointed at failing to secure a contract back home in Wales though remains philosophical about his fortunes.
The British Lion has been without a club since accepting voluntary redundancy when Swansea went into administration in February.
The Wales captain was forced to pay his own way on the summer tour to Australia and New Zealand before landing a private sponsorship with a Cardiff restaurant, owned by former Welsh internationals Mark Ring and Glenn Webbe, for the World Cup after talks with the Neath-Swansea Ospreys collapsed.
"The situation is that when talks broke down with the Ospreys the other regions had pretty much filled their squads," he said.
"I don't know what the future will hold, but I am not ruling out a return.
"What happened was that close to half the professional players in Wales lost their jobs after the Welsh game went provincial so I am by no means the worst off."