Imran Khan, 62, announced that he was becoming a married man, telling a press conference at his 80ha Islamabad estate that "marriage is not a crime".
It was not clear whether the couple had married already.
Khan's bride is former BBC weather presenter Reham Khan, 41, a divorced mother-of-three, who moved back to her native Pakistan in 2013.
Khan has two sons with his ex-wife Jemima Goldsmith, whom he had married in a traditional Islamic ceremony in Paris in 1995 and divorced in 2004. He is noted as Pakistan's only political leader whose public meetings are attended by women, especially the young.
Khan himself said he had waited this long to remarry for the sake of his children.
But his opponents have seized on Reham Khan's high profile and television career as a sign that she was ill-suited to marry the politician, and launched attacks against her character. Photos of her attending a horse race in a knee-length dress were criticised, as were shots of her dancing a tango on a BBC show.