The drones were designed to bring the internet to remote rural areas, complementing its Loon project - a similar initiative using hot air balloons.
However, the solar-powered vehicles have faced technical difficulties and funding challenges.
On Wednesday, blog 9to5 Google revealed Titan had actually shut in early 2016.
A statement from X, the Google division responsible for Titan, confirmed the news.
"Titan was brought into X in late 2015. We ended our exploration of high altitude unmanned aerial vehicles for internet access shortly after," it said.
"By comparison, at this stage the economics and technical feasibility of Project Loon present a much more promising way to connect rural and remote parts of the world."
Google acquired Titan Aerospace in 2014, reportedly fending off a bid from Facebook, which has also been trialling internet-providing drones.
At the time Google said it was "early days", but that "atmospheric satellites could help bring internet access to millions of people, and help solve other problems, including disaster relief and environmental damage like deforestation".
However, after test flights began in 2015, reports alleged that Titan was facing technical difficulties and was running out of money.
In mid-2015, the Titan team also experienced a crash in the Arizona desert which was later linked to a wing fault.
The statement added that "many" Titan staff had been reassigned to different parts of the business, including Project Loon and Wing, a division dedicated to providing drone-based deliveries.
Facebook's internet drones have also faced problems.
The firm's Aquila drone crashed during a test flight in June, prompting an investigation by the National Transportation Safety Board, and an explosion destroyed one of its satellites earlier in 2016.

Both Broughty Ferry lifeboats were called out shortly before midday, with a Coastguard helicopter later joining the search.
Coastguard officers conducted a search on foot of the waterfront area close to the bridge.
The lifeboats were stood down at about 15:00.
A Broughty Ferry RNLI spokesman said: "The inshore lifeboat was launched within six minutes and was quickly in the area of the reported sighting.
"The all-weather lifeboat Elizabeth of Glamis was launched a short time later to join the search.
"Following an extensive search of the area no one was found."

The Nottingham Pram Company made pushchairs and perambulators from a factory in the city.
All the items, including a Victorian pram made between 1880 and 1885, belonged to John Whitby, who ran the firm for 55 years.
The 15 lots sold for £6,700, exceeding the expected £2,500 price tag.
Auctioneers said the collection was "a snapshot of a much-loved company" and was bought by various private collectors across the UK.
The family business was founded in the mid-19th Century by Mr Whitby's grandfather.
More on this story and other news from Nottinghamshire
He took over in 1946, opening a shop on Goose Gate that sold the company's prams, which were manufactured on Alfreton Road, as well as treats for children, such as toys and comics.
Auctioneer Nigel Kirk, of Mellors and Kirk, said the Victorians were "very keen on prams".
"Mr Whitby's father, a builder, and his grandfather were clearly men of considerable importance in Victorian and Edwardian Nottingham, of which they were both appointed freemen," he said.
"When he retired [in 2001], John Whitby had the foresight to carefully preserve everything connected with his grandfather's enterprise.
"For half a century the company was something of a Nottingham institution, selling not just prams but everything for the young child."
The Victorian pram, which beat its estimate and sold for £590, has a "coach-built body" similar to the style used by the Royal Family to transport Princess Charlotte to her christening.
A painted wooden sign, which once hung outside the shop, was also auctioned, as well as catalogues, photographs, toys, comics, shop display material and World War Two posters and souvenirs.
Mr Kirk said: "Some of the items would not have been considered valuable in many people's eyes - for example the trade catalogues from the 1960s, 70s and even 1980s, might have been overlooked in a house clearance.
"However, these lots sold incredibly well, particularly to online bidders."
Google has confirmed it has closed its internet drone project Titan, three years after it bought the business.
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A lifeboat and Coastguard search has been carried out after a report of a body seen in the water near the Tay Road Bridge at Dundee.
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A collection of vintage prams and memorabilia stretching back almost 150 years has been auctioned.