A firework was thrown in to a police vehicle in the Crosland Moor area of Huddersfield on Friday night.
At 10.30pm officers who were conducting routine enquiries parked a marked police vehicle in Devonshire Street.
While unattended, a window of the vehicle was smashed and a firework thrown inside.
Officers discovered the damage and removed the firework before even more damage could be caused.
Det Con Shaun Topham, of Kirklees CID, said: "Although the damage on this occasion was minimal the impact on the local community is far greater.
"The police vehicle has had to be taken out of operational use and as a result one less vehicle is available to attend both emergency and non-emergency calls from the public."
Anyone with information about this incident is asked to contact DC Topham in Kirklees CID on 101.
