The 24-year-old Australian has extended his stay at the club, while countryman Dean Bouzanis - Oldham's No.2 goalkeeper - has also signed a new deal
Midfielder Wesolowski agreed a new contract on Saturday, tying him to the League One club for the next two seasons. Fellow Australian and No.2 goalkeeper Dean Bouzanis has also extended his stay at the Latics, signing a one-year deal after joining half-way through the 2011-12 season on a short-term deal.
Dickov, who is celebrating two years in charge of Oldham, could night hide his pleasure at the Wesolowski's decision.
"I am delighted because James is an integral part of our plans for next season," he told the club's website.
"We saw last season when James and Dean Furman were fit and played alongside each other that there was probably no better central-defensive pairing in League One.
"I would go as far as saying James can be as big as any other signing we make this summer."
Dickov also revealed the Latics withstood considerable interest from rival clubs to retain the 24-year-old's services.
"James received a number of other offers which did not surprise me,” said Dickov, who also described the likes of Weslowski and No.1 shot-stopper Alex Cisak - the third Australian at the club - as the cornerstone of his side.
"He could have been better off financially elsewhere, but he wants to stay with us.
"The great thing about James is that he is fully committed whether in games or training and also to the club as he has shown by agreeing to sign for two years."