Grant, a centre-back, joined the United set-up in January from the Kinetic Academy in London, where he was captain of the team's under -18s side.
Manager Curtis Woodhouse said: "I’m delighted to welcome Kamarl Grant to the club on a loan deal from Sheffield United, a powerful athletic centre back that has a bright future ahead of him and hopefully first team football with us will help his development.
"A big thanks to Sheffield United who have done us a big favour at short notice as we are really light in defensive areas, with Jack Walters out long term and James Williamson picking up an injury on Saturday."
The Holy Blues have also recently confirmed the signings of Tyler Hamilton and Harrison Foulstone.
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