They were forced to hand over property including bank cards, cash, mobile phones and wallets by a man who contacted them on the site Fabguys.com.
Police said during one of the robberies a man was threatened at knifepoint and they believe the three crimes are linked.
Two of the victims were from Reading and one was from Frimley in Surrey.
The first victim, aged in his twenties, arranged to meet a man online at about 22:00 GMT on 9 February in Victoria Park in Reading.
A man arrived, threatened him with a knife, and demanded his phone and bank card, which he used to withdraw money.
Then on 14 February a 56-year-old man arranged a meeting in his home in the Tilehurst area at about 02:00 GMT.
The suspect asked his victim to turn off the lights and light a candle, then demanded his wallet and also stole his bicycle.
Both suspects were black, slim, 5ft 8ins to 6ft tall, and aged 20 to 25-years-old.
A man in his 40s arranged a meeting at midnight on the same day his home in the Warren Rise area of Frimley after getting in contact via the site's app.
When inside his house the suspect robbed the victim of his wallet, mobile phone and iWatch.
PC Jim Bone from Reading CID said: "I would like to remind everyone of the need to be careful when you are arranging to meet people online."
A police spokeswoman added that people using other dating websites could also be targeted.
A spokesman from Fabguys.com said: "We're by far the biggest gay site in the UK so when tens of thousands of men are arranging meets each day, there is the potential for bad encounters.
"We're working with the police to assist them with their enquiry."
He added that tips for safe meetings were offered to users via its website.

The Premier League club also has the option to play all home league and cup matches, as well as any European games, at the national stadium during the 2017-18 campaign.
Spurs are having a new £400m stadium built next to their existing White Hart Lane ground.
The development is due to be completed in time for the 2018-19 season.
"Our season ticket waiting list is over 50,000 so this now also offers us a great opportunity to provide more of our supporters with a chance to see the team play live during our Champions League campaign," said chairman Daniel Levy.
"Importantly, as we know it was our fans' preference, it means that we can play our home matches in London during our season away."
Tottenham's third-place finish in the Premier League qualified them for the group stages of next season's Champions League, which means they will play at least three home matches in the competition.
Their north-London rivals Arsenal hosted Champions League games at Wembley in 1998-99 and 1999-2000.
Football Association chief executive Martin Glenn welcomed Spurs' move, saying: "The increased revenue will help us meet our targets for improving coaching and grassroots facilities and growing participation."
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Three men have been targeted in a series of robberies after using a gay dating website to arrange meetings.
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Tottenham have reached a deal to play their Champions League home games at Wembley next season.