Gerard O'Brien, 54, abused the children at two separate properties, in Ibrox and Cardonald between September 1988 and June 2000.
His two victims, who were just aged four and seven when the abuse began - and cannot be named for legal reasons - told the jury of how they suffered over the years at the hands of O'Brien.
Following a trial at Glasgow Sheriff Court, O'Brien was unanimously found guilty of two charges of using lewd and libidinous practices towards the girls.
Postal driver O'Brien abused his first victim on a number of occasions between September 1988 and September 1991 and his second between June 1993 and June 2000.
Sheriff Alan Mackenzie said: "Their childhoods were blighted."