Money was stolen from Skegness Methodist Church while a funeral was taking place.
The incident happened between 12.15pm and 5pm on August 12 when somebody gained entry to a locked cupboard in a room to the right of the church in Algitha Road.
Two red tins were stolen, which had cash to the value of £65 in.
The suspect got away through the fire exit.
Officers are now appealing for information and anyone with any information should call PC Gary Mathews on 01754 614340 quoting incident number 119 of August 12.