Ex-solicitor Margaret Hampshire and husband Alan admitted faking the will of Martin Blanche, who died in 2007.
The couple then stole Â£23,000 from a cousin of Mrs Hampshire over whom she held power of attorney.
A judge at Nottingham Crown Court jailed them for six months and said it was a "shameful and astonishing crime".
While Mrs Hampshire, 69, was still working as a tribunal judge, the couple forged the will of illiterate Mr Blanche to get their hands on his cottage near Newark, in Nottinghamshire.
The doctored will bequeathed Middle Corner House in Rolleston to Mrs Hampshire's cousin Josephine Burroughs who was also a relative of the dead man.
Mrs Hampshire then used power of attorney to transfer ownership of the home to her daughter.
Mr Hampshire, 67, then took money from Ms Burroughs' account and used it to convert the cottage and a neighbouring property into one larger house.
They moved from Essex to the newly renovated home earlier this year.
The couple initially denied the offences but during a trial last month they changed their plea.
Mrs Hampshire admitted fraud and two counts of forgery - including faking a document to avoid inheritance tax - while her builder husband pleaded guilty to forgery and two counts of theft.
In sentencing the pair, Judge Gregory Dickinson said: "This offending did take place at a time when you held judicial office and when the public was paying for you to fulfil that role, which seems to make your offending all the more shameful and astonishing.
"You abused your knowledge and experience gained as a solicitor, forgetting or ignoring the need to act with integrity.
"Your terrible fall from grace and your age cannot save you from an immediate custodial sentence."
In mitigation, the couple's lawyers said there had been no will and the forgery simply speeded up what would have happened anyway.
Timothy Greene, representing Mrs Hampshire, said she had "fallen a long way" from her respected position in the community and was "utterly humiliated".
A hearing next year will decide if the Hampshires should pay compensation.
An ex-judge and her husband have been jailed for forging a will to inherit a cottage and stealing thousands of pounds for renovations.