WASHINGTON — Representative Duncan Hunter was indicted by a federal grand jury in San Diego on Tuesday after a monthslong criminal investigation into allegations that he spent tens of thousands of dollars in campaign funds on family trips to Hawaii and Italy, private school tuition for his children and even a $600 airline ticket for a pet rabbit.

In a 48-page indictment released by the Justice Department, Mr. Hunter, Republican of California, and his wife, Margaret, are charged with converting more than $250,000 in campaign funds to pay for personal expenses and filing false campaign finance records with the Federal Election Commission.

Mr. Hunter, 41, becomes the second Republican congressman to be indicted this month. Representative Chris Collins, Republican of New York, was indicted on insider trading charges, and announced days later that he had suspended his re-election campaign. The two were the earliest congressional supporters of the presidential campaign of Donald J. Trump.

Mr. Collins, who is accused of passing insider information to his son about a drug company on whose board he served, has said he expects to be “fully vindicated and exonerated.”