Reel Cinema on St Catherines Road, Grantham, was forced to evacuate on Wednesday night after a firework was thrown into their foyer.
The cinema was packed with people, including many children, watching Paddington 2 and Murder on the Orient Express.
Manager Jade Bishop said: “It was about 7pm when my colleagues spotted a person walk towards the doors before throwing a firework, which was lit, into the foyer. There was a loud bang and lots of smoke. It set our fire alarms off and we evacuated both screens. It was a very scary incident for both customers and staff.”
Both the police and fire service attended and investigations are ongoing.
A police spokesperson said: “We received a call at 20:13, under incident number 420 of 15 November. This was a report of a lit firework being thrown into the foyer at Reel Cinema on St Catherines Road, Grantham, which occurred between 7:05pm and 7:15pm. No one was injured.”
Anyone with any information is asked to call 101 with incident reference number 420 of November 15th.