The former striker was part of manager Chris Coleman's backroom staff for the team's recent World Cup qualification campaign.
However, the 38-year-old has now left his post due to "increasing work commitments and family reasons".
Hartson told the Football Association of Wales's official website: "I have enjoyed every moment of my time with Wales. Everyone knows how passionate I am about my country.
"The work I now do as a pundit for the BBC is taking up more and more of my time. With another child on the way I need to spend some time with my growing family."
Hartson won 51 caps for Wales as a player before announcing his international retirement in 2005.