The Prime Minister's comments came after Israeli warplanes hit several targets within Syria. Syria fired back missiles in retaliation.
"When we identify attempts to transfer advanced weapons to Hezbollah, and we have intelligence, and it's operationally feasible, we act to defend it," Netanyahu said in a video aired by top Israeli television networks.
The country's aerial defense systems intercepted one of the Syrian missiles that were launched in retaliation, the Israeli army said.
The army did not elaborate whether any other missiles struck Israeli-held territory, but said the safety of civilians and aircraft was not compromised.
Israel is said to have carried out several airstrikes in recent years on advanced weapons systems in Syria, including Russian-made anti-aircraft missiles and Iranian-made missiles.
They have also carried out airstrikes on Hezbollah bases in Syria.
The Israeli government rarely comments on such operations, and the military statement detailing the air raid and the comments by Netanyahu confirming the operation were highly unusual.
Hezbollah is fighting alongside President Bashar Assad's government in the bloody Syrian civil war.
The Iran-backed terror group is sworn to the destruction of Israel and fought a month-long war with the Jewish state in 2006.
A Syrian military statement said that four Israeli warplanes violated its airspace. According to the statement, the warplanes traveled through Lebanon and targeted a military position in central Syria.
There was no immediate comment from Hezbollah.