Anderson is the first recruit brought in by new boss Justin Edinburgh, who took over on Monday with the club 16th in the League One table.
The 21-year-old joined Palace from non-league Barton Rovers in January 2015, but has yet to play a first-team game.
He had previous loan spells with Doncaster and Bolton and could make his Cobblers debut at MK Dons on Saturday.
"I felt we needed a striker who could stretch defences and worry them with speed and movement, and Keshi can do that," said Edinburgh.
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Northampton Town have signed Crystal Palace striker Keshi Anderson on loan until the end of the season.