The former Goldman Sachs banker was initially director of people, culture and communication at Ocado before being made commercial director.
Ocado claims that over the past few years it has significantly strengthened its operating management team and will ensure there is a "smooth transfer" of Gissing’s responsibilities in the next few months.
Tim Steiner, fellow co-founder and Ocado chief executive, said: "I have worked with Jason for 20 years. Jason has led the development of our brand, and helped shape the culture inside Ocado and the way we are perceived by our customers.
"After our IPO, he focused almost exclusively on marketing and cultural matters before taking on the role of commercial director. He has four young children and wants to spend more time with them. He also has a passion for various environmental and social concerns, and has chosen to focus on these important causes full-time in the future."
Steiner also paid tribute to Gissing’s "daily humour", which was evident in his profile interview with Marketing, where among other things, he joked about "naked delivery drivers" when asked about the company’s marketing plans.
Sir Stuart Rose, Ocado chairman, said: "Jason and Tim started Ocado from scratch just over 14 years ago. Today the business is valued at £3 billion, employing thousands of people, helping consumers around the UK in their busy lives.
"They have laid the foundations of a world-class business. To create a new supermarket in such a competitive market place is an amazing achievement. Jason should be very proud of Ocado. I wish him every success in the future."