They are respectively the second and third senior diplomats to join the opposition to President Bashar al-Assad since the revolt began 16 months ago.
"The ambassador (Abdelatif al-Dabbagh) is now in Qatar," SNC spokesman Mohammad Sarmini told Reuters by telephone, referring to the ambassador to the UAE.
Sarmini said Dabbagh is married to Lamia al-Hariri, Syria's ambassador to Greek Cyprus, who also defected to Qatar in coordination with her husband.
Hariri, a Sunni Muslim from the southern province of Deraa, the birthplace of the 16-month-old uprising, is the niece of Syrian Vice President Farouq al-Sharaa, whose role is ceremonial in a power structure dominated by Assad's Alawite minority sect.
Nawaf al-Fares, Syria's ambassador to Iraq, who is a Sunni tribal figure from eastern Syria, defected to Qatar through Jordan two weeks ago, according to diplomatic sources.