India's Cars24 has seen a big rise in business during the pandemic as people look to alternatives to public transport such as pre-owned cars.
India's popular but unreliable rail networks were shut off completely when the country went into lock-down.
A unicorn refers to a privately-owned start-up firm that is now valued at more than $1bn.
Other start-ups that have gone on to become unicorns, and household names, include Uber and Airbnb.
Covid-19 infections in India have now surpassed 9 million and further lockdowns are being considered.
While trains and buses in India's big cities have resumed services, many commuters are avoiding public transport over fears they could catch the virus while commuting.
This has led to a rise in demand for Cars24, which is based in the city of Gurgaon, near New Delhi.
By the middle of this year, sales had risen 20% from pre-lockdown levels and continue to rise.
"People who did not have cars were looking to own a car due to safety issues while many others wanted to upgrade from two-wheelers," said founder and chief executive Vikram Chopra.
The firm's potential has caught the eye of investment firm DST Global, which spearheaded a $200m funding deal for Cars24 which it announced on Tuesday.
This latest round of financing values the online platform at more than $1bn. Business analytics firm CB Insights says there are now 500 unicorn companies around the world.
Mr Chopra started Cars24 after finding he could not sell his Hyundai Accent, eventually giving it away to a friend.
"The market for used cars and bikes in India is a huge $50bn opportunity," he explained.
DST Global is based in Hong Kong and has backed a number of high-profile tech companies over the years, including Facebook, WhatsApp and Alibaba.
In India, DST has invested in the online shopping company Flipkart, which sold an 80% stake to Walmart two years ago.