The United States says it has begun to deploy troops and Patriot missile equipment to Turkey.
The Turkish government requested the defence system from NATO in 2012 to protect its border with Syria.
In October, five Turkish citizens died when a mortar fired from Syria landed on their home.
The six battery units are scheduled to be operational by the end of January, the BBC reports.
NATO approved the deployment of the surface-to-air missiles early in December, after a request from Turkey, amid "grave concerns" that Syria could use chemical weapons.
Syria has said it would never use such weapons against its own people. But new launches of "Scud-type missiles" against rebel fighters were being detected in Syria, Nato said in mid-December.
NATO Secretary-General Anders Fogh Rasmussen described it as "an act of a desperate regime approaching collapse" and said it emphasised "the need for effective defence and protection of our ally Turkey".
The US, Germany and the Netherlands have agreed to deploy two batteries of Patriot missiles each to be placed under the command of Nato along the Turkish-Syria border.
American personnel and equipment had begun arriving at Turkey's southern Incirlik Air Base and a further 400 personnel and equipment would be airlifted there in the coming days, the US command in Europe, said.