Ms Ingabire said she was “extremely happy” to see her last-born, Rist Shimwa Muyizere, 19, who travelled from the Netherlands to visit her.
The opposition leader is an outspoken critic of President Paul Kagame and his ruling party.
She is not allowed to leave Rwanda without government permission. She says her requests to leave the country have been denied.
Ms Ingabire returned from exile in the Netherlands in 2010 to take part in presidential elections. She was arrested and barred from standing after being charged with threatening state security and “belittling” the 1994 genocide – charges she said were politically motivated.
She was found guilty and sentenced to 15 years in prison but was released in 2018 following a presidential pardon.
In January, the visiting son released a song in Dutch about missing his mother and his hope to see her again.
Ms Ingabire has tweeted a picture of her reunion with her son: