The former Luton frontman, 23, will put pen to paper on a deal until early January on Friday and will be added to the Lions squad which travels to Middlesbrough at the weekend.
Andrew has not been able to hold down a regular first-team place at Selhurst Park this season and has not found the net in eight appearances.
He will join fellow new loan signing, Southampton winger Jason Puncheon, at The Den.
Source: PA
Source: PA