The London-listed company said the disposal is valued at about €24 million ($25.47 million) at the current exchange rate, leading to an expected loss from the sale in the range of €70 million to €80 million.
Headquartered in Moscow, Gotek Group is a Russian packaging producer, and employing around 2,200 people across its business.
The Russian rouble, which crashed to historic lows when Moscow first sent troops to Ukraine on 24 February, slumped to its weakest level against the US dollar in more than five months on Thursday as the currency comes under fresh pressure from the West's price cap on Russia's oil exports.
Against the euro, the rouble was down 0.6% at an 11-week low of 68.72.
Mondi said there was no certainty as to when the deal would be completed given the political and regulatory backdrop.
Its London-listed shares were down about 2% by 09:47 GMT.
In August, Mondi sold its largest plant in Russia - Mondi Syktyvkar - to an investment vehicle owned by Russian billionaire Viktor Kharitonin for RUB 95 billion.
The company had first announced plans to sell its Russian assets in May, as several other companies also flocked out of Russia amid the Ukraine war.