“We all achieved incredible success last season that made history for this great club,” said the 42-year-old.
“Our aim is to continue building on that and I’m already looking forward to the squad’s return for pre-season.”
“Roberto’s quality was clear for all to see when he galvanised the squad last season and helped the club make history, and the owner and board are very pleased he will be continuing his good work,” said Chelsea chief executive Ron Gourlay.
“We all believed he was a young coach with much to offer when we first asked him to take charge and the manner in which he worked with us, the players and all the staff, and the success that followed, made him the clear choice when it came to selecting the person to take us forward in the seasons to come.
“Although he has set the bar very high in the short time he has been in charge, we know that Roberto is the right man to lead Chelsea on to further success.”