An advertising firm that won a $1.25 million no-bid contract with CUNY — which is now the subject of an investigation — is suing the university for being a deadbeat.

Siegelvision Corp. claims the City University of New York and its research foundation stiffed it out of $172,000 in the rollout of a rebranding campaign last year, according to a suit filed in Manhattan Supreme Court.

The Post in April reported that the state inspector general is investigating why CUNY bypassed procurement rules and authorized the sole-source contract through the CUNY Research Foundation, its not-for-profit fundraising arm.

The new “CU” and “NY” logo in ads designed by Siegelvision — accompanied by the slogan “The Greatest Urban University in the World“ — were placed in subways, bus shelters and social media last year.

“On or about Oct. 5, 2017, plaintiff invoices CUNY for $167,800 for its work relating to the rollout of the CUNY campaign,” said the May 29 suit, filed by Siegelvision lawyer Harry Petchesky.

Siegelvision issued three additional invoices on Feb. 24, 2017, July 6, 2017, and July 29, 2017, totaling $4,3777.61 “for out-of-pocket expense for T-shirts and other items,” the suit said.

“All the invoices … were received and retained by CUNY without protest or objection, but no part of the $172,176.61 due thereon has been paid,” the suit claims.

Siegelvision has done ad-marketing assignments for other higher educational institutions, including Cornell, NYU, MIT and The New School.

It also worked for two of CUNY’s 24 schools — John Jay College of Criminal Justice and the Graduate School of Journalism.

Based on the firm’s reputation for boosting “brand identity,” the lawsuit said CUNY officials asked CEO Alan Siegel to develop a proposal to help spruce up CUNY’s brand, which led to the sole-source contract, court papers said.

Christopher Porzio, the attorney identified as representing the CUNY Research Foundation in court papers, did not return messages for comment.