The vessel has departed from the Portsmouth Naval Base in UK.
Following this, HMS Lancaster will take part in Nato taskings prior to any further deployments.
Over the past few years, BAE Systems has supported three major fleet time support periods (FTSPs) of HMS Lancaster.
The maintenance work primarily aimed to upgrade the capabilities and optimise the frigate for future deployments.
As part of the repair works, BAE Systems simultaneously replaced the two diesel generators of the vessel.
The company claimed that the simultaneous swapping out of the generators was a rare undertaking and was completed ahead of its schedule.
The company carried out several emergent tasks, such as hull maintenance and deck repairs along with performing maintenance on the vessel’s mechanical systems including valves and propellers.
Work also included upgradation of the messes, bridges and crew accommodation facilities along with addition of new capabilities across the vessel’s communications, navigation and defence systems.
BAE Systems Maritime Services business asset management head Dean Kimber said: “In preparation for her tasking our teams have delivered three highly successful FTSPs.
“The hard work and expertise of the team throughout these major maintenance and upgrade periods alongside their agile responses to changing requirements and emergent work, means HMS Lancaster will leave Portsmouth optimised for any role the Royal Navy should require of her.”
The RN’s Duke-class frigate HMS Lancaster is a multi-role vessel, primarily deployed for carrying out maritime security patrols.
The warship can also deploy a Wildcat maritime attack helicopter, making it suitable for conducting various challenging defence engagement and security missions.