While clean energy financing had been expected by some to stall in the face of falling oil, gas and coal prices, the study said it rose to £265bn, outstripping investment in new fossil fuel power which stood at £182bn.
The report by Clean Energy Canada - an initiative by Vancouver's Simon Fraser University - also suggests the UK was one of the top five destinations for investment in renewables, attracting £17bn in 2015.
The UK came in below China, the US and Japan - but ahead of India, according to the report, which also found investment in Canada had dropped compared to 2014 and the country ranked eighth in the world.
For the first time more money was invested in clean energy in developing countries, which attracted £120bn, than in developed countries, which saw £117bn poured in to renewable power.
Renewables have been boosted by falling technology costs, with the report suggesting that in the US the unsubsidised cost of wind power has dropped 61% in six year, and solar fell more than four-fifths (82%).
Merran Smith, executive director of Clean Energy Canada, said: "A third of a trillion dollars was invested in renewable power - that's serious money and it set a new record for global clean energy investment, even in the face of stiff competition from cheap fossil fuels.
"The cost of producing clean energy keeps dropping, and the fuel - sun, wind, water - is free.
"There's no wonder clean energy is gaining momentum around the world. It stands in stark contrast with fossil fuel markets, which have seen such high highs and low lows.
"Clean energy is taking off because it offers value that can't be beat - it's local, so it offers energy security. It's a climate solution. It reduces health issues from smog. It's increasingly competitive, and there's big money to be made," she said.
Juliet Davenport, chief executive of green energy company Good Energy, said: " Renewable energy has been an unbelievable success story in the UK and around the globe.
"2015 was record breaking, with a host of big businesses and individuals making the switch to clean energy.
"The UK is a world leader in finance and innovation and should be blazing the trail towards a 100% renewable future.
"Whilst we have seen significant strides in the right direction with investment increasing, the UK Government really needs to get behind renewables and support new technologies which are low carbon, low cost and highly popular with the British public."