Hezbollah has sent thousands of fighters to support Syrian President Bashar al-Assad's troops since Syria's civil war broke out in 2012.
Many of the Hezbollah fighters are concentrated in Damascus and Homs, with smaller numbers in Aleppo and Hama provinces. It fights as a proxy army, mostly under the supervision of Iran's elite Revolutionary Guards.
Hezbollah Deputy Secretary-General Naim Qassem said this week that Sunday's parade was designed to show Hezbollah's backing of the Syrian regime.
"There is a high level of coordination between us and the Syrian leadership," Qassem said, adding that the military parade "was part of our field training."
Syrian state-run media did not comment on the Hezbollah military display.
But Syrian government supporters took to social media to express their anger, saying the parade was "provoking Syria's sovereignty."
Analysts say it is likely Damascus was not pleased by the Hezbollah show.
"This would make some in the [Syrian] regime uncomfortable," said Phillip Smyth, an analyst at the Washington Institute for Near East Policy.
Assad's links to the Hezbollah demonstrates just how complex the Syrian situation is. Assad cannot be regarded as the enemy of Islamic terrorism with friends like those.