Experts say the telescope may have detected a molecule called dimethyl sulfide (DMS) on the planet, which, at least on Earth, is only produced by living things.
However, the researchers emphasize that the detection of the planet 120 light years away is "not strong enough" and more data is needed to confirm the existence of the molecule.
The researchers also detected methane gas and carbon dioxide (CO2) in the planet's atmosphere.
The detection of these gases could mean that the planet K2-18b has a water ocean.
Professor Nikku Madhusudhan, who led the research at the University of Cambridge, told the BBC that his entire team was "shocked" by the data.
"On Earth, DMS is produced only by living organisms. In the Earth's atmosphere, most of it is emitted from phytoplankton in marine environments," Madhusudhan said.
Madhusudhan states that the detection of DMS is not yet finalized and more data is needed to confirm its existence.
This data is expected to arrive after a year.
"If it's confirmed, it's a very big deal. But if we're making such a big claim, I feel a responsibility to get the right results," Madhusudhan added.
Astronomers detect for the first time the possibility of DMS on a planet orbiting a distant star.