The shooting happened at 1:27 a.m. at the Taboo Nightclub and Lounge in the city’s downtown, Cedar Rapids police said in a statement.
"Two individuals are confirmed dead and approximately ten more are injured and receiving medical attention at multiple local hospitals," the department said.
Officers were on routine patrol in the downtown area at the time of the shooting and responded quickly to the scene.
As of 5 a.m., police said the scene was secure and there was no threat to public safety.
No details on what led to the shooting or who fired the shots were immediately released.
Detectives were interviewing witnesses as the investigation into the shooting continued.
Authorities asked anyone who was at the nightclub at the time of the shooting or with knowledge of the incident to contact Cedar Rapids Police at 319-286-5491 or Linn County Crime Stoppers at 1-800-272-7463.