The agency has been briefed to provide production and AV support for a series of management forums. It will organise several events a year, each for around 220 people.
The aim of the events is to encourage teams from various Sellafield sites to share best practice knowledge.
Paul Morey, Glasgows’ managing director, said: "We are extremely pleased to be working with such a well respected organisation and we will work very closely with Sellafield Ltd in order to deliver a catalogue of successful events over the next three years.
"These are high profile events with executive director participation and where the technical support must be at the highest level."
Sellafield Ltd is the company responsible for for delivering decommissioning, reprocessing, nuclear waste management and fuel manufacturing activities on behalf of the Nuclear Decommissioning Authority (NDA).