About Us

Buying and selling real estate in New York City is unlike any other market in the world!

The Diaman Group provides full-service real estate assistance to buyers and sellers of admirable Manhattan and Hamptons properties. We provide our clients with exceptional expertise and confidentiality when buying and selling property.

Whether you are a first time buyer or have bought and sold many times before, you will quickly discover that each real estate transaction is as unique as the property itself. The path to a successful transaction can be very complex at times and we specialize in making your transition as smooth as possible!

Who We Are? What We Do? Why We Are Successful?

• We listen to you!
• We provide the unbiased, straight-forward advise you deserve!
• We formalize a plan based on our market expertise and market research!
• We guide you and answer all questions that arise!
• We are sensitive of the financial and emotional issues affecting you!
• We are easily accessible and always get back to you promptly!
• We reach your goals!
• We work together!
• We put your best interest first!
• We are PROUD to make these promises to you!

Search for luxury Manhattan and Hamptons real estate in one place.

Meet our Team

Our diverse team brings a wealth of expertise across various real estate specializations.

John Diamantopoulos
President & Broker
John Diamantopoulos
President & Broker

Real Estate Broker / Owner Professional

Read From Our Blog

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Discover what our clients have to say about their experiences with us.

John Diamantopoulos is my real estate agent in New York City and will continue to be. I will continue recommending him and only him to anyone that I know who is thinking about purchasing in Manhattan. I must say thank you to for making my transaction as effortless as possible in what we all know can be a difficult market to enter. Thank you very much for your time. Best Regards,
by Dave Natale
, The Rolling Stones
John more than fulfilled our expectations in that our apartment, in a down market was sold in a week and a half and at a price considerable above the listing price. We were previously listed with another firm for months without any activity or offers. Similarly our purchase of a larger apartment was handled expeditiously and in a matter that gave us great confidence. John’s knowledge of the Coop process was very impressive and made the process very smooth.
by Dr. James and Theresa R
Over the past 25 years, I have sold several real estate properties and had the fortunate experience of dealing with top notch brokers. However, the experience in dealing with John in the sale my property in NYC exceeded my previous expectations and set a new standard for other professionals in the field. He sold my property at an incredible price in less than 2 weeks. If there is a Real Estate school, were the craft and the art are topics for discussion, John should be the professor! He understands sales, negotiations and the value of building contracts based on value as well as trust. Without hesitation I recommend him to any seller in the current Bust or Boom economy.
by Michele S
In a down market John did a wonderful job and in record time. In our case he was able to sell our apartment while comparable apartments in and around our building remained on the market unsold. John was able to get a higher price for our home while the other comparable apartments were actually lowering their prices below what we received! John listened to what we wanted and knew just how to accomplish it. If we ever buy or sell again we would use John without hesitation!
by Howard S

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