The cupro-nickel, rhodium-plated medal features the head of Queen Victoria and the legend VICTORIA + D + G + BRITT + REG + F + D + IND + IMP (Victoria, by the Grace of God, Queen of Britain, Defender of the Faith, and Empress of India) on one side, while the other displays the legend MAGNUS · PRIORATUS · ORDINIS · HOSPITALIS · SANCTI · JOHANNIS · JERUSALEM · IN · ANGLIA (Grand Priory of the Order of the Hospital of St. John of Jerusalem in England) along with five equally sized circles in a cross holding individual heraldic icons supported by sprawling St John's Wort. These are the St Edward’s Crown, the shield of Great Britain, two icons of the Order of St John in England, and the cipher bearing the feathers of the Prince of Wales. The "only British medal to retain the head of Queen Victoria on a current issue", the image utilized is based on a bust of the queen created by Princess Louise, Duchess of Argyll. The medal's design has been largely unaltered since creation, though the script has changed from gothic to seriffed capital letters and the original practice of naming the recipient on the medal gradually ceased except in New Zealand, but the metal composition has evolved from its original silver to various silver-plated base metals before reaching its current composition in 1966.
The medal is suspended from a ribbon that is 1.5 inches wide with five equally spaced stripes, of black and white. Where additional services beyond those required for the award have been performed, the ribbon may display bars and laurel leaves. In most countries (Including New Zealand and Canada) a recipient is awarded a silver bar for every five years up to three silver bars, beyond which all silver bars are removed and a gilt bar is put on the medal for each five years. At the fifty two year mark, the recipient is awarded a laurel leaf and all bars are removed. All bars are represented on the undress ribbon by appropriately coloured Maltese crosses, while the laurel leaf is also used on the undress ribbon.
The medal is typically rewarded to recognise efficient service of appropriate duration. The length varies by location, with current terms for the United Kingdom, Australia, Canada, New Zealand and South Africa set for 12 years, while other territories require 10. Other forms of conspicuous service have also been recognized with the medal.
In the United Kingdom, the Service Medal is after the Solomon Islands Independence Medal and before the Badge of the Order of the League of Mercy in the order precedence. In Canada, the medal is after the Ontario Provincial Police Long Service and Good Conduct Medal and before the Commissionaire Long Service Medal.
In 2010, the Order of St John England and the Islands decided that time spent as a Cadet, (previously ONE year for every THREE YEARS proficient as a cadet), would not count towards the Service Medal.