The pair of orbiters launched on a Russian-built Soyuz, will boost to six the number of satellites in the Galileo constellation and bring the network a step closer to becoming operational.
Blastoff took place from Europe's Kourou space centre at 1227 GMT as scheduled, after a 24-hour bad weather delay.
Live footage showed the rocket lift off before shedding its four boosters and faring -- the nose cone that protects the craft in the early stages of flight.
At three hours and 47 minutes after launch, the satellites are set to separate into free-flight orbit at an altitude of 23,500 kilometres (14,600 miles) above Earth.
The 5.4-billion-euro ($7.2-billion) Galileo constellation is designed to provide an alternative to the existing US Global Positioning System (GPS) and Russia's Glonass, and will have search and rescue capabilities.
Four Galileo satellites have been launched before Friday, -- the first pair in October 2011 and the second a year later. The constellation will ultimately comprise 27 satellites and three reserves.
The launch of the latest two orbiters, dubbed SAT 5 and SAT 6, had been delayed for over a year due to what the European Space Agency (ESA) described as "technical difficulties in the setting up of the production line and test tools".
Arianespace said Thursday it had signed a deal with the ESA to launch 12 more satellites "from 2015 onwards".
The ESA has previously said that 18 satellites should be able to provide initial navigation services to users "by mid-decade", with full services "scheduled for the decade's end".
In March last year, the ESA said Galileo's first four test satellites had passed a milestone by pinpointing their first ground location, with an accuracy of between 10 and 15 metres (32 to 49 feet).
For its ninth liftoff from the Guiana Space Centre Friday, the Soyuz rocket carried a total load of 1.6 tonnes, including the two satellites weighing 730 kilos (1,600 pounds) each.