Thackeray's statement came against the backdrop of probe by multiple agencies into actor Sushant Singh Rajput's death and its media coverage which was seen by some as a deliberate campaign to target Bollywood.
"Moves to finish off the film industry or shift it elsewhere will never be tolerated," a statement from the Chief Minister's Office quoted Thackeray as saying at a meeting with multiplex and theater owners.
Mumbai was not only the country's financial capital but also its entertainment capital, he said.
"Bollywood enjoys a following across the globe. The film industry generates huge employment. In the last few days, attempts have been made to malign the image of the film industry by certain quarters which is painful," he said.
The BJP government in Uttar Pradesh recently announced a plan to create a film city in that state to woo film-makers.
Thackeray informed cinema and multiplex owners at the meeting that the state culture department has prepared a Standard Operating Procedure (SOP) regarding reopening of cinema halls which have been closed for over six months due to coronavirus pandemic.
The decision about reopening cinema halls will be taken at the earliest after the SOP is finalized, he said.
"The government is positive about it. Entertainment industry is a means to boost the state's economy and the government is keen to restart it," the chief minister said.
"In a cinema hall, people are in one room for nearly two hours and hence we want to ensure complete cleanliness and sanitization as well as physical distancing. There is a need to ensure that only 50% seats are occupied," he said.
Culture minister Amit Deshmukh said a priority will be given to the safety of film-goers, though reopening of cinema halls will boost the economy.