Said to be the largest incident of its kind, the Air Force Secretary Deborah Lee James said it emerged during an investigation into alleged illegal drug possession.
Nuclear arsenal, however, remains secure, he said.
James said the officers range in rank from second lieutenants to captains in the cheating that occurred around last August and September.
"As part of that investigation, we discovered just a couple of days ago late in the weekend that 34 missile launch officers at Malmstrom Air Force Base in Montana were involved in the compromise of answers to a launch officer proficiency test," he said.
There are about 190 officers overseeing readiness of nuclear weapons systems in Montana. As such, the scandal has touched nearly 20 per cent of its force.
Describing this as "absolutely unacceptable" behaviour, and completely contrary to core values in the Air Force, James said he has great confidence in the security and the effectiveness of US' ICBM force.
"This was a failure of some of our airmen. It was not a failure of the nuclear mission," he said.
Before going public with the investigations, he briefed Defense Secretary Chuck Hagel on allegations that several dozen ICBM officers cheated on their proficiency tests. Hagel had just returned from visiting ICBM officers in Wyoming.
"Hagel was deeply troubled to learn of these allegations, and he strongly supports the aggressive steps the Air Force is taking in response to them," Pentagon Press Secretary Rear Admiral John Kirby said.
"Having just returned from visiting with ICBM officers in Wyoming, Secretary Hagel understands the importance of their mission and the necessity that it be executed according to the highest standards of professionalism. He will be following the issue closely," Kirby said.
Air Force Chief of Staff General Mark A Welsh yesterday said the commander of Global Strike Command ordered a STRATCOM-validated proficiency test be administered to all missile crew members and all three of our missile wings.
The Air Force Global Strike Command commander also directed that each of US missile wings receive a limited nuclear surety inspection focused on operation crew procedures in the near future.