Nicola Kent abused her position of trust and stole the victim's bank card before going to cash machines in disguise and withdrawing large sums of money.
The 41-year-old mother-of-three was jailed for ten months over the offences which she committed while working at Castleton Care home in Leeds.
Kent drained the account of £5,500 before the victim checked his bank statement and discovered almost all of his savings were missing.
Duncan Ritchie, prosecuting, told Leeds Crown Court how Kent had worked in the care industry for many years and had been employed at the home since March last year.
Her manager regarded her as a hard worker and she was a mentor to other members of staff.
The court heard the victim was vulnerable after being diagnosed with early onset dementia and also suffered from cancer.
Mr Ritchie said he had a bank card and cash when he was moved to the home.
The defendant was responsible for taking custody of his belongings and keeping them in a safe place for him.
The offending came to light in September last year when the victim was due to leave the home and found that his bank card was missing.
He checked his bank statement and found that there had been 11 cash withdrawals from his account which he knew nothing about.
The balance of his account in August last year was just £91.
Each withdrawal was for £500 from a cash machine in Leeds.
Mr Ritchie said: "Effectively the account had been virtually emptied."
Police were contacted and they recovered CCTV footage of someone making the final cash withdrawal using the victim's card.
The person making the withdrawal was wearing a headscarf but police were able to track the suspect's movements as she walked away.
Kent was identified as the culprit when footage showed her removing the headscarf.
Officers spoke to the manager of the care home who said Kent had been experiencing personal problems and had been taking time off work.
The defendant had been staying at the home of a work colleague after breaking up with her partner.
Kent was interviewed at a police station but denied stealing the money despite being shown the CCTV footage.
After leaving the police station she went to her friend's home.
Kent told her that she had been suspended from work and had been interviewed by police on suspicion of theft.
Mr Ritchie said Kent's friend then refused to let her stay at her house and made her leave the property.
The woman decided to put Kent's belongings in a bin liner and discovered £3,500 in cash when she emptied drawers.
Police were informed and Kent was interviewed for a second time.
Mr Ritchie said: "This time she admitted what she had done.
"She said she had financial and personal difficulties, that she had been in debt and that she had been depressed."
Kent, of Heights Drive, Armley, Leeds, pleaded guilty to one count of fraud and one of theft.
Mr Ritchie read a statement to the court on behalf of the victim describing the impact of the offending upon him.
He said: "I do not sleep well and suffer from anxiety.
"It is on my mind so much.
"I don't want to go out at all and have stopped seeing friends.
"I am out of pocket with regards to money. It has stopped me being able to do things I want to do.
"I have cancer and I am 70 years of age. I want to be able to enjoy every day and the defendant has taken that away from me."
The prosecutor said Kent had placed her work colleagues under suspicion by denying the offending.
Stuart Field, mitigating, said Kent had no previous convictions.
He said Kent carried out the offences due to financial pressures following the breakdown of her relationship with her partner.
Mr Field said the defendant was ashamed of what she had done and intended to repay the money in full to the victim.
Jailing Kent, Judge Simon Phillips QC said: "Your denials would have placed suspicion on others at the care home.
"I have heard from Mr Field, information about your situation at the time following on from the break-up of your long-term relationship with the father of your three children.
"That did not stop you from taking a holiday to Greece during this time.
"You took his possessions and you did so without any justification whatsoever.
"This was deliberate targeting of a victim who you knew to be vulnerable."