Williams is a former director of James Brearly & Sons and has worked in north Lancashire and Cumbria for the past 20 years, first with Rathbones and then James Brearly since 1999.
Principal acquired border in January and the combined business now manages in the region of £1.6 billion of assets for around 4,000 clients.
Border chief executive officer, Peter Lever, said: "We are delighted that Adrian is joining our team of specialist investment managers. He is well known to both private clients and in the professional community in the area and I am confident he will help us build on the success that Border has had both in Kirkby Lonsdale and in Harrogate in recent years.
