Jeffrey Silver wants $13 million from the pair for a "vicious scheme" to destroy his "reputation, career and very life," the New York Daily News reported Thursday.
Silver once dated Bernstein's current wife, Christine Kuehbeck. Silver was arrested last year and accused of stalking Bernstein and Kuehbeck, but the charges were dropped.
"It was pretty outrageous, the thing that was done to me," Silver said Wednesday.
Bernstein's lawyer branded Silver's suit "an outrageous falsehood" filed "to extract money from an internationally respected journalist and author and to slander a wonderful woman." He said the couple may countersue.
Bernstein won a Pulitzer Prize with fellow reporter Bob Woodward for their Watergate reporting that led to President Richard Nixon's resignation.