Ewa Nosalska molested the young stranger before another shocked passenger yelled on the driver to call police.
The bus pulled in and was emptied before the 42-year-old was eventually arrested.
Nosalska today admitted to a sexual assault charge at Glasgow Sheriff Court.
The crime occurred on February 9 this year in the city’s East End.
Nosalska – who had been drinking – had initially tried sitting on the laps of male passengers.
She then moved beside the teenage boy who was on the upper deck of the bus.
READ NEXT: Man hiding in loft with guns said he would shoot cops who came near
Fiscal Gail Campbell described to the court what Nosalska then done to him.
She added: “The boy did not say anything to her but tried to push her away.
“Another passenger saw what was happening and shouted on the driver.”
After the bus was evacuated due to her conduct, Nosalska again started pestering the boy.
She fled the scene before being traced and arrested a fortnight later.
Pat Campbell, defending, told the court Nosalska has “no recollection of the matters at all”.
Sentence was deferred pending background reports until next month by Sheriff Joan Kerr.
Nosalska was remanded and placed on the sex offenders list.
