A short-term visit initially scheduled for April has been allowed on August 21.
Radio Svaboda has learnt it from Natallya Pinchuk, the wife of the imprisoned human rights activist.
A long-term visit can be held only in November.
It should be reminded that Byalyatski, the head of Viasna human rights centre, was sentenced to 4.5 years in a medium security penal colony and confiscation of property in November 2011. He was accused of tax evasion on a large scale. Byalyatski's prosecution started after Lithuania and Poland revealed information about his foreign bank accounts to Minsk under mutual legal assistance treaties.
Byalyatski said at the trial the money on his accounts had been spent on human rights activity.