The wing-back scored Chelsea's second goal himself 20 minutes later, taking his time to fire past goalkeeper Bernd Leno after being found in acres of space by Mason Mount.
Lukaku, who never scored a league goal for the Blues in his first spell, showed why Chelsea were prepared to break their spending record to bring him back to the club seven years after he left London.
The Belgian provided the Blues with the kind of muscular presence in attack they have lacked since the departure of Diego Costa in 2017, both when running at Arsenal's defence and holding the ball up with his back to goal.
Only a reflex save by Leno denied him a second goal when the German palmed Lukaku's point-blank header onto the bar with 15 minutes to play.
Arsenal, lacking several key players through injury and illness, rarely threatened to disrupt Thomas Tuchel's well-drilled side, who kept another of their trademark clean sheets and could afford to start with star names such as N'Golo Kante, Timo Werner and Hakim Ziyech on the bench. (Reuters)

SWAN Honours Ezeonwuka, 40 Years After Building Rojenny, Nigeria’s First Private Stadium
Man City need to 'step up' as striker's goal run ends
'People are afraid' - why 'juggernaut' Arsenal are team to beat
Aspinall requires further tests on eye injury in UK
Real Madrid impress but Vinicius tension grows - Clasico talking points
Rooney says struggling Liverpool lack leadership
NOC To Host FinalIOC Advanced Sport Management Course Module
4 Teams Lock Horns For N10m Tiger 5-Aside Football Battle In Awka
Nezianya, Odikpo, Balepo, Ndukuba, Chukwuleta For SWAN @60 Veterans’ Awards
Anambra FA Crisis: Igbokwe, 61 Years Old Football Administrator Protests Arrest, Detention
Gala European record thrills Osimhen
La Liga: 'I am enjoying football at Barca', Rashford eyes permanent move
Rangers International going, going . . . (63,273 views)
Amaju Pinnick: A cat with nine lives (54,480 views)
Second Term: Amaju Pinnick, Other NFF Heavyweights Home to Roost •How Pinnick Broke the Jinx (52,429 views)
Current issues in Nigerian sports: Matters arising (52,036 views)
Sports Development: Zenith Bank on the zenith (52,015 views)
Missing $150,000 IAAF Grant: Solomon Dalung’s Hide and Seek game (51,989 views)
Gov. Abdullahi Ganduje’s solid footprints, commitment to sports development in Kano State (51,818 views)
NFF Presidency: Pinnick, Maigari, Ogunjobi, Okoye in Battle for Supremacy (51,398 views)
Olopade, BET9A wave of revolution in NNL (50,512 views)
Commonwealth Games 2018: Shame of Muhammadu Buhari, Solomon Dalung (49,055 views)
Ibrahimovic’s Man U exit: Whose decision is it? And in whose interest? (47,491 views)
John Mikel Obi: Segun Odegbami’s Outrageous Call! (46,954 views)