Putin's approval was the final step needed to pass the legislation, which RIA Novosti said would come into effect from Jan. 1, 2013.
According to Reuters, 52 Russian children are currently in the process of being adopted by US families. Those adoptions will now be halted.
"There are lots of places in the world where living standards are higher than they are here," the BBC quoted Putin as saying when he signed the bill into law on Friday.
"Are we going to send all our children there? Perhaps we should move there ourselves?"
The bill is widely seen as Russia's retaliation for the US Magnitsky Act, which recently introduced sanctions against Russian nationals suspected of human rights abuses. (It is named for Sergei Magnitsky, an anti-corruption lawyer who died in a Russian prison in 2009; despite suspicious circumstances, no one has ever been convicted over his death.)
Russian lawmakers originally drafted a "tit-for-tat" response blacklisting a number of US citizens, Reuters said, but then went further and added the ban on adoptions and on certain non-governmental organizations with links to the US.
According to RIA Novosti, as the legislation now stands, US and Russian agencies are forbidden from organizing American adoptions; alleged US rights abusers are barred from Russia and their Russian assets frozen; political NGOs that receive US funding are banned, and US citizens are barred from working for politically active NGOs in Russia.
Rights group Amnesty International says the new law will have a "chilling" effect on Russian civil society, while others have expressed concern for the impact on the thousands of children awaiting adoption in Russia's already crowded orphanages.
Putin has promised to sign an order for better "support mechanisms" for parentless children, the BBC reported.