The agency picked up the business following a four-way pitch, managed by COI, against Tequila\, Agency.com and True Digital.
Dialog will be responsible for web-build duties on two accounts for HQRG, which handles all of the Army's specialist recruitment. These are for Camouflage, the Army's youth recruitment programme, aimed at 13- to 17-year-olds, and Army Jobs, its main recruiting body for non-infantry recruitment.
The Camouflage work will also involve a TV campaign that Dialog will create alongside its sister agency, Publicis.
Simon Marshall, the chief executive of Publicis Dialog, said: "I'm delighted that our capabilities have been recognised, and that we can continue to partner Publicis in creating effective and engaging communications for the Army during one of its more challenging periods."
Mark Bainbridge, the marketing director of HQRG, said: "Camouflage is a programme of which we are immensely proud for its responsible attitude to engaging young people with the Army proposition."