"Everything is fine, I am in my bed. It gives me an opportunity to rest. It is a small heart problem, nothing serious. The beast is strong," he told AFP, laughing several times despite a tired voice.
Asked when he would be discharged, he responded that he didn't know and that it depended on the doctors, and went on to cite a line from a bawdy French song: "Doctors are like priests, you have to take their word for it."
A party source had earlier linked the hospital visit to stress from a highly publicized political blow-up with his daughter and party chief Marine Le Pen, saying it was related to recent "emotional shocks".
Known for his hair-raising comments, Jean-Marie Le Pen vexed his daughter by reiterating his long-held view that the Nazi gas chambers were merely a "detail of history" and making other controversial remarks.
"He's really pissing me off," was the reported response of Marine who launched a media blitz against her dad last week.
The 86-year-old party founder eventually pulled out of upcoming regional elections, anointing his granddaughter Marion Marechal-Le Pen to take his place.
He is also facing disciplinary action from the party.
Under Marine Le Pen, who has tried to clean up the party's racist image since taking over the reins in 2011, the FN has enjoyed a series of election successes, notably coming first in last year's European elections.