The Strictly Come Dancing champion wed Johnston in Harpenden, Hertfordshire yesterday (December 21), according to the St Albans Review.
The couple held their nuptials in the St Nicolas church in the town, where Johnston reportedly grew up.
An image from the day shows Judd's friends and fellow McFly members Tom Fletcher, Danny Jones and Dougie Poynter leaving the church.
Judd, Jones and Poynter were all best men for Fletcher's wedding in May this year.
Judd and Johnston had been dating for six years before he proposed in May. They met while Johnston, a professional violinist, performed with the band on their 2005 tour.
McFly previously revealed that they want to collaborate with Jessie J, calling the 'Price Tag' singer "amazing". They also said that they want to continue writing music for One Direction.