The Londoners have won only one of their last seven games in all competitions and coach Andre Villas-Boas paid the price for the form slump when he was sacked on Sunday.
"Eddie knows the club and many of the players," said Di Matteo as he took charge of the side ahead of Tuesday's FA Cup Fifth Round replay at second-tier Birmingham City.
"I have worked with him for many years and it was easy for him to slot in for us and give us a hand until the end of the season," the 41-year-old Italian told the club's website.
"He is a Chelsea man and I want some passion from people who care about this club and this is one of our jobs as well, to transmit that to the team."
Newton previously worked under Di Matteo at West Bromwich Albion and the pair were midfield colleagues in the Chelsea team that beat Middlesbrough in the 1997 FA Cup final.
Both men scored a goal on that occasion at Wembley and it is ironic that Di Matteo and Newton will relaunch their partnership in an FA Cup tie.
The former Italy midfielder said everyone at Chelsea had gone through a tough time.
"It has been a very difficult 24 hours for a lot of people at the football club," Di Matteo explained. "Andre has brought some very good, positive ideas and changes and we will benefit from his changes.
"I enjoyed very much working with him and we will remain friends for the rest of our lives but I will have to move on for this club and try my best with the players we have here.
"We need to regroup for sure. Today I have mostly spoken to the players individually to try to get them in the right frame of mind for the task ahead and that is our job now."
Di Matteo could make alterations to the team against Birmingham who sprang a surprise by holding Chelsea to a 1-1 draw at Stamford Bridge last month.
"I have a good idea of the team I want to play in the replay but I am still uncertain about one or two positions and there might be a few changes," he said.
