The Democratic National committee's rules and bylaws committee voted 19 to 8 to restore the northern state, after earlier voting to reinstate Florida, which also broke party rules by bringing its primary forward to January.
Clinton, who won the primary, in which Obama's name was not on the ballot, will get 69 delegates, who will each only have half a vote in nominating the party's presidential nominee.
Obama will get 59 delegates, who will also have half a vote under the plan.
But Clinton's senior advisor Harold Ickes, who had argued that Obama should get no votes, said the former first lady's supporters had been hijacked.
"Mrs Clinton has instructed me to reserve her rights to take this to the credentials committee," Ickes said.
The committee is due to meet in July as preparations accelerate for the party convention.
The rules and bylaws panel earlier voted 27-0 for the compromise Florida plan, which will give primary winner Clinton a net gain of 19 delegates to the convention but leave her well behind Barack Obama in the total delegate count.
The plan will see all the state's delegates , and superdelegates (top party officials) restored, but they will each have only half a vote at the convention in Denver in August to crown the party's presidential challenger.
At a fiercely contested meeting at a Washington hotel, the committee earlier rejected Clinton's bid to have the Florida delegation seated in full.
Clinton's angry supporters chanted "Denver, Denver" demanding the row be taken to the party convention in August and "Madame President" "Madame President."