Berylson's association with the Lions began in 2006, with the club confirming his passing in a statement on Tuesday evening.
"It is with a collective broken heart and the deepest of regret that we announce the passing of our beloved owner and chairman, John Berylson," it read.
"John, who turned 70 last month, lost his life in a tragic accident on Tuesday morning, and the thoughts of everyone at the club are with his wife, Amy, his three children, Jennifer, James, and Elizabeth, and the rest of the Berylson family.
"John’s sudden and tragic passing will unquestionably impact all those who were fortunate to have known him. He was a truly great man, incredibly devoted to his family, and a person of such remarkable generosity, warmth, and kindness. He lived a storied life, one full of colour and joy, and was infinitely thoughtful of others with an endless desire to share his immense knowledge and experiences to help people.
"Under John’s passionate leadership and guidance, Millwall Football Club has enjoyed tremendous success and stability. Since first becoming involved in the club in 2006, he has presided over some of the greatest moments in Millwall’s history, and his influence in providing the platform for those was immeasurable. John continued to speak eagerly about the new season and his vision for the future, and any success moving forward will be in his memory and honour. It will be his legacy.
"John revelled in the club’s underdog status and mentality. He related strongly to such values and identity and adored Millwall supporters. He was fiercely loyal to all his staff, and both they and the fan base will miss him beyond measure.
"For those who wish to pay their respects, a book of condolence, which will be shared with the Berylson family, will be opened at The Den from 11am on Wednesday 5th July.
"Those who cannot make it in person to The Den will be able to sign an online book of condolence, which will be available on millwallfc.co.uk in due course. Rest in peace, John, and thank you. You were loved and adored."
Millwall made significant strides under Berylson in recent years, recording four successive top-half finishes during the past four seasons.