The parliament voted 94 to nine in favour of airstrikes against the IS, Xinhua reported.
Denmark had announced last Friday that it would send fighter jets to join the fight against the IS in Iraq.
In addition, Denmark will send troops to northern Iraq as the US wants Denmark to contribute to the training of Iraqi and Kurdish security forces.
The Danish soldiers would not be sent for battle but would assist in training processes, Danish Prime Minister Helle Thorning-Smidt has said.
The prime minister said that the Danish fighter jets would only participate in the fight against IS on Iraqi territory as the country itself has requested for military support.