The leader later deployed Attack Mode for the second time with 25-minutes to go, but the 28-year-old again took the lead, once more clearing the Season 2 champion.
Vandoorne remained unchallenged to the chequered flag, fronting a 1-2 result for Mercedes as de Vries finished in the runner-up spot, overtaking third-placed finisher Buemi after finding himself with an energy adavntage at the end of the race.
Behind, Rene Rast took fourth place for Audi ahead of Sam Bird who completed the top five in his final race for Envision Virgin Racing.
Lucas di Grassi took sixth and was followed by Jean-Eric Vergne in seventh, Alex Lynn in eighth, Antonio Felix da Costa in ninth and Edoardo Mortara who completed the top 10.
The Swiss-Italian’s ROKiT Venturi Racing team-mate, Felipe Massa, finished in 16th and revealed at the end of the race that he will be leaving the Monegasque marque at the end of the season.