The US has stressed its support for Georgia joining Nato after a brief war in August between Tbilisi and Russia over the breakaway region of South Ossetia.
Despite strong US backing to bring Georgia and Ukraine into the alliance, Germany, France and some other members opposed the move, fearing it might anger Russia.
Nato has already expanded to include a number of eastern European countries that were once part of the Soviet-controlled Warsaw Pact, despite pledges in the early 1990s not to move quickly toward Russia's borders.
The ceremony followed meeting betwen in the Oval Office with Jaap de Hoop Scheffer, the Nato sectretary-general, who noted that Albania and Croatia would be the 27th and 28th members of the alliance.
"Their accession will be a boon for Nato, as it will strengthen our common effort to safeguard and promote security and stability," de Hoop Scheffer said.
He said their joining Nato would be "a vivid demonstration that southeast Europe can shed its tragic past."