Kim Aris, who for years had only received sporadic, second-hand updates about his 81-year-old mother, said he had spoken directly with Suu Kyi.
"Hearing her voice again means more to me than words can express," Aris said in a statement.
A spokesperson for Myanmar's military-backed president said on social media that Aris had spoken with Suu Kyi by telephone through Myanmar's embassy in London, sharing separate photographs of the pair.
Suu Kyi, a Nobel Peace Prize winner, has been detained since February 2021, when Myanmar's military ousted her elected government and arrested civilian leaders in early-morning raids.
The coup sparked nationwide protests that evolved into an armed resistance movement, plunging the impoverished country into a civil war that has killed about 100,000 people and displaced millions.
Suu Kyi was moved to house arrest in April following a military-engineered election that installed coup leader Min Aung Hlaing as president.
She is serving an 18-year prison sentence on charges ranging from incitement and corruption to election fraud and violating a state secrets law, all of which she denies.
"She remains unjustly detained and a single conversation cannot restore the years taken from her or the rights she is still denied," Aris said on Thursday.
"Regular, direct and private family contact and independent medical access must be guaranteed."
For years, little information emerged about her health and wellbeing, raising concern among supporters and foreign governments.
In August, Suu Kyi met a representative of the International Committee of the Red Cross - a visit that Aris had described at the time as a positive sign.
The military-backed government on Monday released rare photographs of Suu Kyi meeting officials who delivered her books and a letter from Britain's King Charles.
"Above all, my mother and all political prisoners must be released immediately and unconditionally," Aris said.
"Freedom is not a favour to be granted or a concession to be negotiated."
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