Udaltsov was released in early August after serving a 4.5-year term for organizing protests that turned violent on the eve of Vladimir Putin’s inauguration on May 6, 2012.
Dozens were charged in a string of cases known as the Bolotnaya case which rights groups criticised as politically motivated.
In an interview with the opposition-leaning Dozhd television channel on Wednesday, Udaltsov said “the investigation won’t see me testifying against someone else.”
He also said the summons could be intended as a form of “exerting moral pressure on me.”
Less than a month after his release, Russian media reported that investigators wanted to question Udaltsov again.
“Seems like the investigation must have forgotten something over the five years,” Udaltsov wrote in a follow-up Twitter post.
Most of those convicted in connection with the Bolotnaya case have since been released. One has been transferred to a mental health facility, while the trial of another activist is still continuing, according to the Mediazona news website.