The former Northampton Town striker has joined the League One outfit on a one-year deal, and Allen is confident that he will be a success at the Priestfield Stadium.
The 47-year-old told the club's official website: "It is my gut feeling that he will do well in a Gillingham shirt, playing for the club that he loves.
"Opposition teams cannot handle him or deal with him. I'm sure, with the passion of our supporters, that he will respond on the big stage called Priestfield.
"He will be a very valuable member of our squad, on and off the field."
Akinfenwa scored 17 goals in 51 appearances last season.