The latest English Private Landlord Survey shows that 17% of landlords own five or more properties but account for 49% of all private tenancies.
By comparison, 45% of landlords own a single rental property.
The research also found that 6% of landlords own rental property through a company, up from 4% in 2018.
John Minnis Estate Agents said the figures point towards a changing landlord market, with newer investors increasingly viewing property as part of a broader investment strategy.
Official figures show the typical landlord is currently most likely to be male, aged 55 or over and based in London, the South East or East of England, with many owning one or two rental properties alongside full time employment.
John Minnis, founder of John Minnis Estate Agents, said: "For many years the typical landlord was someone approaching retirement who bought one or two properties as a pension investment. While those landlords remain incredibly important, the profile of new investors entering the market is becoming much more diverse."
"Tomorrow's landlord is likely to be younger, more commercially minded and far more strategic in how they invest. They're treating property as part of a wider financial plan rather than simply a retirement asset, and they're increasingly willing to invest wherever the strongest long-term opportunities exist rather than just close to home."
Minnis added that investors are increasingly carrying out research and seeking specialist advice when making property decisions.
"Property ownership has become much more sophisticated. Investors are carrying out more research, taking specialist advice and thinking carefully about where demand will be strongest over the next decade rather than simply buying the nearest available property."
He added: "The strongest landlords are those who take a long-term view. Successful investment isn't about chasing the highest headline yield or reacting to short-term market movements. It's about buying quality property in areas with strong fundamentals and holding those investments over time."
