Troopers say the incident happened Jan. 31 at the State Correctional Institution-Mercer.
The Associated Press is not naming the suspects because police say they won't be charged unless and until crime lab tests confirm the presence of drugs.
Police say the 45-year-old Pittsburgh woman had the balloons in her mouth when she kissed the 46-year-old inmate that afternoon.
Police say prison officials recovered the balloons days later from the inmate's bowel movement.
Police plan to charge the inmate with possessing contraband - in this case, an illegal drug - and to charge the woman with furnishing drugs to an inmate.