US Rep. Chris Collins is expected to plead guilty in Manhattan federal court Tuesday to insider trading charges, The Post has learned.

The Buffalo-area Republican — who previously declared his innocence — will enter a change of plea on Tuesday.

Additionally, the congressman’s son, Cameron Collins, and co-defendant Stephen Zarsky are expected to cop to unspecified charges on Thursday, according to court documents and a source close to the case.

The case centers around an Australian biotech company, Immunotherapeutics, where the lawmaker served as a member of its board of directors.

Prosecutors claim Collins called his son with an inside stock tip after the company failed a key drug trial.

Cameron allegedly dumped his stock and passed the news to Zarsky, leading him to sell off his shares too.

The trio faced a slew of fraud, wire fraud, securities fraud and related charges.

Lawyers for the Collinses could not be immediately reached Monday. Zarsky’s attorney declined to comment.

The change of heart comes weeks after Collins, his son and Zarsky entered pleas of not guilty on Sept. 12 to an updated indictment filed by prosecutors in August.

Collins told reporters outside the downtown courthouse that day he was unsure whether he would seek re-election to the seat he’s held since 2013.

The Buffalo lawmaker made the comments after saying he looked forward to being “exonerated” of charges.

“I have not decided if I’m gonna run for re-election,” the pol, who represents New York’s 27th District, told reporters. “I can tell you, I’m confident if I do, I will win.”

Collins was re-elected last year despite the indictment hanging over his head.

Additional reporting by Bob Fredericks