The 20-year-old, who was part of the England Under-20 squad that won the World Cup this summer, has agreed to a third loan spell away from the North-East having spent the previous two seasons with Coventry and Barnsley.
Armstrong has also made 21 appearances for his parent club having made his debut in the Premier League three years ago.
Bolton boss Phil Parkinson told bwfc.co.uk: “We are delighted to bring in Adam.
“He’s a good young player with great potential and we are looking forward to working with him.”
Port Vale will assess defenders Kyle Howkins and Joe Davis before their home game against Stevenage.