Prime Minister Narendra Modi asked India's 1.3 billion citizens to observe nine minutes without electricity at 21:00 local time (16:30 GMT) on Sunday.
He urged them to "challenge the darkness" of Covid-19 by lighting candles and lamps.
Millions responded, lighting up the night sky in a show of unity.
"Salute to the light of the lamp which brings auspiciousness, health and prosperity, which destroys negative feelings," Mr Modi tweeted at the time of the vigil.
But critics have dismissed the event as a stunt, arguing it distracted from the health and economic crisis caused by the coronavirus pandemic.
Mr Modi imposed a nationwide lockdown on 25 March, announced with little warning, leaving millions stranded and without food.
There have been more than 3,500 confirmed infections and around 100 deaths from Covid-19 in India, the latest figures from Johns Hopkins University say.
The true figures, however, are thought to be far higher. India has one of the lowest testing rates in the world, although efforts are under way to ramp up capacity.
There are fears that a major outbreak in the country - one of the world's most densely populated - could result in a humanitarian catastrophe.