The former Australia international signed a short-term deal, Al Gharafa confirmed on their website, saying he had been recruited until the end of the season. The campaign will only run into May for Al Gharafa if they reach the AFC Champions League knock-out stage.
Kewell, 34, was in contention to make his debut in Saturday's Qatar Stars League match against Al Sadd.
The golden boy of Australia's golden generation, Kewell had been without a club since leaving Melbourne Victory at the end of last year's A-League season for family reasons.
Many expected him to return to the A-League, with Perth Glory apparently interested in bringing him back, while he had also been hopeful of finding a club in England last summer.
Kewell began his career at Leeds in the late 1990s, moving on to Liverpool and Galatasaray before returning Down Under in 2011.