Pat Kember said in a videotape broadcast by Aljazeera that her husband "was a peaceful man who went to Iraq with his companions on a charity mission".
Kember expressed her concerns about her 74-year-old husband's health, pointing out that he "has not got his medicines on him".
There is still no information on the fate of Kember, American Tom Fox and Canadians James Loney and Harmeet Singh Sooden who were abducted in Baghdad on 26 November.
The men were part of a delegation for the Christian Peacemaker Teams, a body which dispatches volunteers to crisis areas in a bid to reduce armed conflict.
A group called the Brigades of the Swords of Righteousness claimed responsibility for the kidnapping.
It released pictures of the four men on the internet and set a deadline of 10 December to kill them unless foreign troops withdrew from Iraq and Iraqi prisoners were released.