The Brazilian midfielder sustained the injury during Tuesday night's victory against Tottenham, his second appearance since recovering from an ankle problem.
Manager Eddie Howe had expressed concern, noting Guimaraes had no prior hamstring issues.
His absence is a significant blow to Newcastle, who have a poor win record in league matches without him.
The injury leaves Howe with limited senior central midfield options ahead of their FA Cup clash with Aston Villa.
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