Hookway, 72, used the money to fund private health care for his wife Shirley, who he lives with at his comfortable refurbished 16th century home nearby.
In 2004, the couple moved from Reading to their property in Malton, North Yorkshire, which they completely renovated.
They previously spoke about how they spend a "fortune" decorating their country home each Christmas.
Hookway was jailed for 20 months on October 29 for swindling his bosses, the Howard family, out of £78,670 by manipulating the refund system and putting visitor's cash his pocket rather than the till.
He pleaded guilty at York Crown Court to nine charges of theft by employee.
Paul Nicholson, prosecuting, said Hookway worked in the ticket office and stole an average of £1,660 a month, taking between £31 and £668 a day.
Mr Nicholson said accountancy checks at the estate revealed something was amiss in August 2018. Investigators saw Hookway carrying out the thefts while they were checking CCTV footage from the admissions booth.
When he was arrested at work on August 26, 2018, he had £155 in his wallet and £75 in an envelope at his side.
The court heard police could not investigate if he had been stealing before 2012 because the till records before then had not been kept.
Julian Goode, mitigating, said his client was remorseful for his actions and handed in a letter which he said showed that the stolen money "could be repaid immediately".
Mr Goode said: "This was not an offence to provide him and his wife with a lavish lifestyle. This was motivated by his wish to help his wife."
Judge Simon Hickey said it was only right Hookway repaid the money and set an assets confiscation hearing on March 4.
He told Hookway: "You are a well-off man and you chose to behave in this way and to steal from this establishment."
A Castle Howard spokesperson said: "We are pleased that this matter appears to be concluded and we will not be making any further comments."
As well as starring as Brideshead in both the 1981 TV and 2008 film adaptations of Evelyn Waugh's novel Brideshead Revisited, Castle Howard has been used as a backdrop in many films and TV shows.
The castle has featured in the 1995 film The Buccaneers. Peter Ustinov's 1965 film Lady L and as Lady Lyndon's estate in Stanley Kubrick's 1975 film Barry Lyndon.
It doubled as the Kremlin, in Galton and Simpson's 1966 film The Spy with a Cold Nose. Rooms and was used for indoor scenes in the series Death Comes to Pemberley in 2013.
The castle and its grounds were also the setting for the Bollywood film Shaandar and the 2006 film Garfield: A Tail of Two Kitties. The location also featured in the 2018 Arctic Monkeys video Four Out of Five.
Pop star Ellie Goulding also held her wedding reception at the stately home earlier this year after tying the knot with art dealer Caspar Jopling at York Minster.