Thomson Airways flights from Manchester to Florida, USA, and from Glasgow to Cancun in Mexico, took off as scheduled at 09:40 BST.
Boeing, which produces the planes made of carbon fibre and plastic, claims it is the world's most efficient aircraft.
Thomson had planned to use the 787s from May, but all 50 were grounded in January over faulty batteries.
Singer Alesha Dixon greeted passengers arriving at Manchester Airport on Monday.
Chris Browne, managing director of Thomson Airways said the introduction of the "revolutionary" aircraft was a "major milestone" for operators.
Each aircraft can carry up to 291 passengers and fly as high as 38,000ft (11,500m).
Boeing claims the combination of lightweight materials and new engines from General Electric and Rolls Royce means that the Dreamliner is 20% more fuel efficient than equivalent aircrafts in use and also 60% quieter.
The firm had originally hoped the plane would go into commercial service in 2008, but it has been dogged by production difficulties.
Japanese carrier All Nippon Airways operated the first commercial flight in October 2011.
Boeing's worldwide fleet of Dreamliners were grounded and deliveries halted for three months, however, after a battery on an All Nippon Airlines 787 caught fire and a malfunction forced another flight to make an emergency landing.
Flights using the aircrafts were reintroduced in April after new batteries were fitted.
Thomson Airways are planning to take delivery of eight 787s in total.
British Airways has taken delivery of the first two of 42 Dreamliners ordered over the next 10 years and Virgin Atlantic is scheduled to get the first of its 16 Dreamliners in September 2014.
The first long-haul flights from the UK using the troubled 787 Dreamliner aircraft have taken off.