Born in Ramela, Guarda, Portugal, Inês Monteiro first experienced success in professional athletics at cross country competitions: she won the silver medal in the junior race at the 1998 European Cross Country Championships and took the gold the following year. On the world stage, she reached the 5000 metres final at the 1998 World Junior Championships in Athletics and competed in the junior race at the 1998 IAAF World Cross Country Championships. She improved her position for the 1999 edition in Ireland, finishing in thirteenth.