Both were on their way to Saudi Arabia to perform Umrah, a pilgrimage to Makkah that can be undertaken any time of the year.
BNP Senior Vice-Chairman Tarique, accused in a number of cases at home, has been staying in London since 2008 after securing bail from the Supreme Court during the past military-backed caretaker government.
It is their second meeting since then. The first time the two met was during Khaleda’s 2011 London visit.
An Emirates flight carrying the BNP chief landed at Prince Mohammad bin Abdulaziz International Airport at around 3:30am (local time) on Sunday, Khaleda's Press Secretary Maruf Kamal Khan said.
He said Tarique boarded the same flight at the Dubai International Airport with his mother.
Hundreds of party activists turned up at the airport to greet Khaleda and her son Tarique.
The BNP chief and her entourage are staying in Saudi Arabia as the guests of King Abdullah.
After Medina, Khaleda will go to Makkah and perform Umrah.
She will spend the night of Shab-e-Qadr saying prayers at Al Masjid Al Haram.
The former prime minister is scheduled to return home on July 26 before the Eid-ul-Fitr.