The bridge to the Bailey and the steps up the Keep are currently off limits and Wakefield Council is looking at options to restore those areas.
The Castle’s visitor centre is also now closed and the council is exploring ideas for it in the future.
Coun Les Shaw, Cabinet Member for Culture, Leisure and Sport, said: “Sandal Castle is a key monument in the district and is open to visitors this summer.
“We hope everyone continues to support this fantastic heritage site we have on our doorstep.
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“We apologise for any inconvenience caused by some parts of the Castle being closed, but we need to ensure that the site is safe.
“We are looking at options and how to restore these and hope they will reopen as soon as possible.”
Visitors to the Castle are also asked not to seek alternative routes up the side of the Keep and other parts of the grounds.
It can be dangerous due to the slippery and uneven ground and can cause damage to the monument.
However, plenty of summer activities are still planned.
The Friends of Sandal Castle have organised a free concert by the West Yorkshire Police band on Sunday, July 24, between 1pm-3pm.
More information about the Castle and events taking place is available at www.wakefield.gov.uk/castles