"I wrote to President [Vladimir] Putin but we got an answer [saying] that they are going to sell that kind of weapon to the Syrians," Sharon said on Tuesday.
"We worry about that and we don't think that that should have happened," he added.
Israel and the United States have both expressed disquiet about the sale of the Russian-made surface-to-air SA-18 missiles, fearing they could end up in the hands of Hizb Allah, the Damascus-backed resistance group in Lebanon.
"We are not pleased with the sales of weapons to Syria, particularly sophisticated weapons that Russia intends to sell to Syria, weapons that may end up in the hands of terror organisations," Sharon said.
Syrian President Bashar al-Asad, who met with Putin in Moscow last month, has said any missile system would be for defensive purposes.