Villa have signed goalkeeper Pierluigi Gollini, midfielder Aaron Tshibola and defender Tommy Elphick since being relegated from the Premier League.
"We're certainly looking for a striker," Di Matteo told BBC WM 95.6.
"And maybe some more attacking players, depending on how the next few weeks go and which players are going to leave."
Di Matteo has a first-team squad of 30 with only Rudy Gestede, Jordan Ayew, Gabby Agbonlahor and the injury-hit Libor Kozak providing senior striking options.
Villa have been linked with Chelsea striker Patrick Bamford and Bristol City's Ivory Coast international Jonathan Kodjia as they attempt to make an immediate return to the top flight.
"You could probably name 15 players that have been linked with us but I'm very pleased with the players we've brought in - I think we've done some good business there," Di Matteo said.
"But my attention will now focus on outgoings. I would like to trim the squad - it's too big for my liking, so there will be some movement now."
Villa start the league season at Sheffield Wednesday on Sunday, 7 August.
Aston Villa boss Roberto Di Matteo says he wants to sign another striker ahead of the Championship season but must trim his squad first.