"It's great that we are attracting players of Mandy's calibre to the club," manager Kelly Chambers said. "Mandy will add to our young squad."
Centre-back Van den Berg, 26, led her country at the 2015 World Cup in Canada and has been capped 75 times.
She played 13 times for Liverpool this season as they finished fifth in Women's Super League 1.
Netherlands captain Mandy van den Berg has joined Reading Women from Liverpool on a permanent deal.