Moroccan defender Achraf Hakimi scored the second goal for Paris St-Germain as they opened their Champions League campaign with victory over Borussia Dortmund.
Mbappe scored from the penalty spot on 49 minutes after his shot was handled by Nicklas Sule.
PSG doubled their lead when Moroccan defender Achraf Hakimi combined well with midfielder Vitinha.
The French side are in Group F with Newcastle and AC Milan.