Wards nine and 10 have been shut to new admissions and relatives are being told to avoid visiting patients amid concerns about the spread of Norovirus.
The bug causes diarrhoea and vomiting which usually lasts for 72 hours and is easily spread among people who are already ill.
An investigation is under way to establish the cause of the infection.
An NHS Lanarkshire spokesman said: “Restrictions are in place at wards nine and 10 in Wishaw General Hospital due to suspected Norovirus.
“Infection prevention and control measures are being taken to reduce the spread of any infection and ensure the wards are back to normal as soon as possible.
“We would like to ask for the co-operation of visitors who can take some simple actions to minimise the impact of Norovirus.
“People should not visit hospital if they have symptoms of suspected Norovirus and they should wait until they have been clear of symptoms for at least 48 hours as they may still be contagious.”