A statement on Al-Rayyan's website said: "Nilmar of the club Villarreal is coming to Doha to completed negotiations... He will be a great addition to the attack."
Nilmar was always likely to leave El Madrigal this summer following the club's relegation from the top flight in Spain at the end of a season in which injury restricted him to just 13 league starts.
However, a potential move to the Middle East is a surprising one.
The former Internacional forward, who was a member of the Brazil squad at the last World Cup, turns 28 years old on Saturday, and has attracted interest from clubs both in Europe and back in his homeland.
Should he move to the club which finished third in the 12-team Qatari league last season, he will add to a Brazilian contingent that already includes former Middlesbrough striker Afonso Alves and ex-Besiktas midfielder Rodrigo Tabata.