John A. Zaccaro, the husband of former vice-presidential candidate Geraldine A. Ferraro, pleaded guilty today to a misdemeanor charge of scheming to defraud a mortgage broker and a securities firm in a real estate transaction.

According to the grand jury indictment, Zaccaro, 51, submitted false documents exaggerating the sale price of five apartment buildings, inflating his net worth from $4 million to $21.6 million and altering the appraisal of the properties in an effort to obtain financing.

Manhattan District Attorney Robert M. Morgenthau said Zaccaro stood to gain $333,000 in brokerage commissions and an 8 percent interest in the properties as a result of the deal, which fell through when an attorney for Zaccaro's client noticed the discrepancies and canceled the loan application.

No evidence was produced that Ferraro was involved in or knew of the various business deals under invstigation. But questions about her husband's finances dogged her campaign and his plea could affect any plans she had to run for office in the future.

Zaccaro, tanned and wearing a gray suit, was booked and arraigned in criminal court. During the short proceeding, State Supreme Court Justice George Roberts asked him whether he understood the charge. Zaccaro, flanked by three attorneys, replied, in a barely audible voice, "Yes." The judge then asked, "How do you plead?" Zaccaro replied, "Guilty."

The scheme-to-defraud charge carries a maximum sentence of a year in prison and a $1,000 fine, but Roberts said that, in accordance with Zaccaro's agreement with the district attorney, he would not impose a jail term at the sentencing, scheduled for Feb. 20.

The plea was the culmination of a four-month investigation of Zaccaro and his business associates that was prompted, prosecutors say, not by his wife's candidacy but by a routine federal audit last spring of loans made by the credit union of the Port Authority of New York and New Jersey.

In a statement distributed by his lawyers after the court appearance, Zaccaro said he hoped the plea would end "the inquiries and the microscopic attention given to my personal and business affairs since July . . . . My lawyers have advised me that since my client and I withdrew the loan application, since no one but I was injured and since I received no benefit, they felt that they could successfully defend this case."

He added, however, that "in light of the nature of the charge and in order to spare my family the publicity of prolonged legal proceedings, I wish to conclude the matter and try to return to a private life."

Ferraro did not accompany her husband to the arraignment at his insistence, according to Zaccaro attorney Arthur Liman. In a statement issued from their home in Queens, Ferraro said that her husband "committed a judgmental error" but that "he has freely admitted his mistake, and for this I am proud of him."

Ferraro, the first woman nominated to a major-party U.S. presidential ticket, said the guilty plea ends "the difficult period my husband has endured stemming from my historic candidacy." She characterized him as "a decent, honorable man, and today's events do nothing to change him in the eyes of his family and friends," she said. "We love him very much."

New York politicians today appeared uncertain as to whether Zaccaro's plea would affect his wife's possible challenge to Sen. Alfonse M. D'Amato (R-N.Y.).

"They're probably opening champagne bottles at Elizabeth Holtzman's office" one New York congressman said, noting that Holtzman, now Brooklyn's district attorney and almost certainly a candidate in the Democratic primary, "can come off as squeaky clean."

But Gov. Mario M. Cuomo said: "One will never know for sure what effect it has on her . . . . I guess in the real world some people would use it as a reason not to vote for an individual, but I'm not sure that's relevant," he said. "When your husband or spouse is accused of a crime, does that mean that you are impaired in your ability to function? I'm not so sure."

Norman Adler, political action director of District Council 37 of the state, county and municipal employes union, one of the most powerful in the state, said: "It doesn't sound great, but it's not a knockout punch . . . . It shouldn't have a major effect. A lot of New York Italians are sick and tired of having their ethnicity used as a weapon. A lot of sympathy would come to the surface."

At a news conference before the arraignment, Morgenthau said the investigation of Zaccaro's real estate deals "would have proceeded in the normal course of events" regardless of Ferraro's candidacy. He said that, despite extraordinary news media attention, the candidacy did not change the focus or targets of the probe.

As prosecutors described the complex tangle of events, last spring federal auditors uncovered several questionable loans during a routine examination of the books of the Port Authority credit union. Among the improper transactions was a $550,000 loan to John DeLorenzo, a real estate developer, who was not a member of the credit union and thus not entitled to a loan under federal regulations.

The 1983 loan was for the purchase of a Manhattan apartment building. Zaccaro and Ronald Harnish, then counsel to the credit union, acted as brokers for the sale, sharing a $100,000 commission. Zaccaro's real estate firm was hired to manage the building.

Harold Farrell, a disbarred attorney and a business associate of Zaccaro's, was indicted today and pleaded not guilty to charges that he paid kickbacks to credit union employes who helped arrange the loan. Morgenthau, answering allegations by Farrell that Zaccaro directed him to pay the kickbacks, said that, under New York law, "You have to have corroboration of an accomplice's testimony."

Zaccaro has denied knowing about the kickbacks.

When the loan question was referred to the district attorney's office in September, investigators began to look through the records of other deals involving Zaccaro, Farrell and DeLorenzo.

In 1983, Farrell, Zaccaro and Robert Wolk, another broker, formed the Teig Corp. to seek financing for DeLorenzo's purchase of five Queens apartment buildings. According to the indictment handed down against Zaccaro, he submitted to the David Cronheim Mortgage Co. a false contract of sale listing the purchase price on DeLorenzo's sales contract at $15.5 million instead of the correct $11.98 million.

Zaccaro also altered a copy of an appraisal of the buildings, changing its date and address, and submitted the false document to Prudential-Bache Securities Inc. in an effort to obtain financing, the indictment said. In a loan application to the securities firm, he declared his net worth to be $21.6 million when in fact, according to the indictment, it "was no more than $4 million as he well knew."

Financing for the deal collapsed when Prudential-Bache found out about the falsification from DeLorenzo's attorney, Morgenthau said. Zaccaro lost an $80,000 deposit he had borrowed from the estate of an elderly Queens woman that he was overseeing as a court-appointed guardian. Zaccaro was forced to repay the loss and later was removed as conservator of the estate after the incident was publicized.