Damon Lee, 54, from Grantham Close, Sandhurst, and Rocky Frankham, 37, from Easthampstead Road, Wokingham, each pleaded guilty at Reading Crown Court on Tuesday to one count of fraud by false representation.
Lee was sentenced to three years and two months imprisonment, and Frankham was sentenced to two years and eight months.
Between April 6, 2011, and August 13, 2012, the pair regularly visited a 77-year-old man at his home in Crowthorne and persuaded him he needed building work carrying out to repair his property.
In total, they stole £42,950 from the vulnerable victim by charging him for completely unnecessary work.
PC Barry Johns, from Local CID at Loddon Valley police station said: “The victim was vulnerable and was taken advantage of due to him living alone and having very limited short term memory.
“The work purported to have been carried out in exchange for the money was unlikely to have been required in the first place or carried out at all.
“After a lengthy investigation, I am pleased with the result, which can now start to bring some closure to the victim and his family.”
Chief Inspector Robert France, local police area commander for Wokingham, said: “In this case a vulnerable and elderly man was targeted in a sustained manner.
"We should make no mistake that this is not poor quality work but a deliberate and significant fraud in which £42,950 was extracted from the victim.
“We only became aware of this offending when concerned family members brought it to our attention, and it is unfortunately too often the case that victims either do not realise they have been subjected to a crime or do not feel able to come forward.
“I would ask anyone who is concerned about a friend, family member or neighbour to contact either the police on 101 or Trading Standards, with whom we work very closely.
"We take all reports seriously and your call may be crucial to protecting a vulnerable member of our community.
“Trading Standards are able to provide advice on a range of issues, including obtaining the services of a reliable company for building or maintenance work.
"Their website address is www.westberks.gov.uk and includes a link to the Trading Standards supported Buy with Confidence scheme.”
Anyone concerned about anyone who may be a victim of this type of crime should contact police on 101 or for emergencies on 999. Trading Standards can be contacted on 01635 519930.