Ian Squire was one of four Britons taken at around 2am local time on October 13 when militants stormed the community they were living in.
Alanna Carson, David Donovan and Shirley Donovan have all been released following negotiations.
In a statement, the Foreign Office said: "We are supporting the families of four British people who were abducted on October 13 in Nigeria, one of whom was tragically killed.
Relatives of the three people who have been released said they were "delighted and relieved" that the trio returned safely.
They said in a statement: In a statement, the families of the four hostages said: “Alanna, Ian, David and Shirley were kidnapped in Nigeria some three weeks ago.
“We are grateful for the support received by the British high commission and help from the Nigerian authorities in negotiating their release.
“We are delighted and relieved that Alanna, David and Shirley have returned home safely. Our thoughts are now with the family and friends of Ian as we come to terms with his sad death.
“This has been a traumatic time for our loved ones who were kidnapped and for their families and friends here in the UK. We would therefore ask that the media respect our privacy as we come to terms with the news. We will not be making any further comment.”