"I affirm the State of Qatar's full support for Lebanon and its brotherly people against the brutal attacks they are being subjected to," the emir said on social media platform X.
"I have directed rapid action and the provision of all necessary resources to provide humanitarian and relief support to all displaced persons and those affected by this aggression."
Israel has shifted the focus of its operation from Gaza to Lebanon, where heavy bombing has forced hundreds of thousands to flee.
The bombing has killed more than 1,000 people, according to Lebanon's health ministry.
"The failure of the international community to stop the war on Gaza was a green light to expand the conflict," Sheikh Tamim said.