Shortly after his Bharatiya Janata Party (BJP) won the elections, Mr Modi tweeted, in a mix of Hindi and English, that "India has won! Good days are coming".
The tweet sparked excitement among his followers and some of his opponents also congratulated him on the microblogging site.
The response was only expected because Mr Modi and his team had used social media in innovative ways to maximise their reach among the young voters during the campaign.
Many publications around the world said that 2014 marked "India's first social media elections".
A year later, the Indian PM appears to have strengthened his social media outreach with new accounts on Instagram, China's Twitter-like service Weibo and Viber chat forum.
He even replied to a recent Dubmash video on one of his speeches.
Mr Modi is among the five most followed politicians on Twitter with 12.5 million followers. Others in the top-five club are US President Barack Obama and Pope Francis.
Looking back at his "social year", it appears that Mr Modi prefers social media over TV, print interviews or press conferences.
Analysts say he did not share good relations with the media during his long tenure as the chief minister of Gujarat state and "his current strategy reflects that".
When opposition parties criticised his government's land acquisition bill, he used Twitter to hit back.
On foreign policy matters, the PM appears to have forged "good personal relations" with world leaders through Twitter diplomacy.
He congratulated British PM David Cameron after he won the elections, tagged US President Barack Obama in tweets and held "Twitter conversations" with Australian PM Tony Abbot and Japanese PM Shinzo Abe.
During his visit to Japan, Mr Modi used Twitter to highlight his close friendship with PM Shinzo Abe. The CNBC called it "Twitter bromance".
He chose Twitter to thank Mr Obama for writing his short profile for Time magazine.
Mr Modi and his team also carefully selected different languages to tweet, often depending on his travel itinerary.
He tweeted in Japanese during his visit to Tokyo, used French when in Paris and wrote in Mandarin while travelling in China.
And it's no secret that he loves selfies. He even convinced an "often rigid" Chinese Premier Li Keqiang for a selfie.
The jury is out on the impact of Mr Modi's global Twitter outreach, but most pundits agree that he has certainly made a mark on "social media diplomacy".
Dr Athar Zafar of the Indian Council of World Affairs, a Delhi-based think tank, says "it's too soon to judge Mr Modi's overall foreign policy".
"His Twitter exchanges with world leaders have certainly established that the Indian PM is modern and social media-savvy. Twitter is great as a 'soft diplomatic tool' but real deals are made on the talking table," he says.
Back at home, he reaches out to millions almost every day.
He uses Twitter to wish people on festivals, exchanges messages with celebrities and even with his cabinet colleagues.
Dr Zafar says Mr Modi and his team keep his social media accounts ticking 24/7 and that allows people to stay connected with the PM.
"This is in stark contrast with previous PM Manmohan Singh who was known for speaking less frequently. So there was an appetite and Mr Modi appears to have filled that gap," he says.
But too much social media presence has its own risks.
Apart from getting tags like Feku (liar) and Gappu (idiot) by his rivals, Mr Modi has also faced Twitter backlash over his "controversial statements".
Speaking at an event in Seoul, Mr Modi recently said Indians liked migrating abroad because they were not happy with their own country.
And the past year also saw what many described as "Modi memes".
His visit to the Terracotta Army museum in Xian sparked humour on Twitter, but he did not respond to the memes.
"That is something Mr Modi lacks, he needs to respond to humour. That could be his challenge for the next year," Dr Zafar adds.
When Narendra Modi won the general elections a year ago, the UK's Financial Times called him "India's first social media prime minister".