Mohammed Ismail, of Hilden Street, Bolton, assaulted two women, one as young as 17, after sitting next to them on trains.
He touched the two victims on two different trains leaving Manchester Piccadilly.
The 39-year-old sat next to the women on both occasions, despite numerous other seats being available.
Manchester Magistrates’ Court heard how he assaulted a 17-year-old on a journey from Manchester to Bolton last year.
The teenager told the court that she was wearing shorts on a hot summer’s day when Ismail began stroking her thigh.
She claims she has flashbacks of the trauma and feels scared every time a stranger sits next to her.
The teenager, who cannot be named for legal reasons, said: “He sat quite close to me which I thought was quite strange as both the other two seats were free and if there is space, people usually tend to distance themselves.
“He was so close he was touching me.
“He touched my thigh and rubbed it up and down from the top of knee to the pelvis area – so, the full length of it.
“I moved his hand away and he put his hand back on it again.”
She added: “I felt so vulnerable and trapped. I was in disbelief really, you don’t think this kind of thing is going to happen to you.
“I felt so vulnerable and trapped. I was in disbelief really, you don’t think this kind of thing is going to happen to you.”
Victim, aged 17
“Since this happened I don’t sleep very well. I have flashbacks and panic attacks about what happened,” she continued.
“Sometimes it feels like only yesterday that it happened.”
On the second occasion, the sex pest started speaking with a young woman on a journey between Manchester and Preston.
The fiend got so close she could feel him rubbing his own thigh as he squeezed up against her.
Speaking to the court, the victim said: “He asked me for the time which I thought was quite weird as when you board a train you tend to know the time.
“After that he didn’t speak but after a while he started asking me questions like where I had been and where I was going.
“I tried to keep my answers fairly abrupt but he then asked me a few times if I was getting off at Bolton.
“The questions were actually more unsettling than the touching because it almost felt like a script.”
Both women identified Ismail from an identity parade, but he claims it was a case of mistaken identity.
Following a one-day trial, magistrates rejected his claims and convicted him of two counts of sexual assault.
Ismail has been found guilty of two counts of sexual assault and has been banned from travelling on trains without authorisation from police.
He had three previous convictions for historic sexual offences, including assault of a female under the age of 16.
Ismail will appear for sentencing at Manchester Crown Square Crown Court on Monday 27 May.