A jury found 68-year-old Francis Cassidy guilty of subjecting a young girl to abuse from her ninth birthday until the day before her 19th birthday.
He was arrested after a second woman, aged 22, told police she had also been indecently assaulted.
The women – who cannot be named for legal reasons – both gave evidence during a trial at Livingston Sheriff Court.
Cassidy, of Toronto Avenue, Livingston, had denied two charges of lewd, indecent and libidinous behaviour against the younger girl and two charges of indecent assault involving each victim.
The jury heard evidence that he repeatedly exposed himself to the younger girl, groped her over and under her clothing and forced her to commit sex acts on him.
Sheriff Susan Craig warned Cassidy to put his affairs in order in the expectation that he would be jailed. She ordered that Cassidy’s name be added to the sex offenders register.