Back in India, billboards above the traffic jams of New Delhi bear the image of Priyanka Chopra, a Bollywood star and former Miss World who is fast becoming a household name in the United States, also adorned with Modi's jewels.
But on Thursday, officials at the nation's central investigative agency announced it was looking for Modi as law enforcement officials fanned out to raid his jewellery stores and other businesses in Mumbai and New Delhi.
Central Bureau of Investigation (CBI) officials told reporters the agency had on Feb. 4 issued a lookout circular in the country for Modi, who they say had left four weeks earlier.
Modi, who has a net worth of some $1.8 billion according to Forbes magazine rankings, has not yet responded to the allegations and could not be reached for comment.
His flagship company, Firestar Diamond, has said it had no involvement in the case.
The setback in Modi's climb to fame and fortune was abrupt, even by the rough-and-tumble standards of one of the world's fastest growing major economies.
During an interview with Reuters in November, the famously soft-spoken Modi discussed his love for art, poetry and paintings. He also spoke of his wife and three children with whom he lives in central Mumbai.
Asked how he planned to raise funds to add new stores, he seemed unconcerned.
"All options are open," he said, sitting in his cavernous Mumbai office. "We could use internal accruals. We can take loans from banks or we could do an initial public offering."
But last month, India's second-largest state-run lender filed a criminal complaint with the CBI that accused Modi and others of defrauding the bank and causing it a loss of 2.8 billion rupees ($43.8 million).
Then on Thursday, the same bank, Punjab National Bank, publicly alleged that Modi was involved with a much larger fraud case: $1.77 billion from a single branch stretching back to 2011.
The news was a shock for the circles in which Modi moved.
As recently as last month, he was at the World Economic Forum in Davos. Indian media carried a group photograph with Prime Minister Narendra Modi in the foreground and Nirav Modi, who is no relation, grinning between rows of Indian business leaders behind him.
"Top industrialists invited him home to display his collections," said a Mumbai investment banker at a U.S.-based firm who has worked directly with Modi's company. "There was a personal touch in everything he sold. Nirav Modi is a brand."
A senior member at Bharat Diamond Bourse, a Mumbai-based industry body with more than 13,000 members, sketched a similar profile of Modi.
"In one of the industry meetings in 2013 he said that when people wear a Cartier ring they don't say it's a diamond ring, they say it's Cartier," said the member, who did not want to be named. "He always wanted people to say they are 'wearing Nirav Modi'."
Modi grew up in Antwerp, Belgium, in a diamond-dealing family. In 1990, at the age of 19, he moved to Mumbai, according to the November interview.
Nine years later, Modi started his own company, Firestar Diamond Ltd., selling loose stones. He employed fewer than a dozen people at the time. By last year, the number was more than 2,000.
He said he came to realise the margins were better in retail.
Firestar Group, the parent company Modi controls as a majority shareholder, saw its revenue grow over three years from 103 billion rupees (about $1.6 billion at current rates) to some 147 billion rupees ($2.3 billion) by the 2016-17 fiscal year, according to figures previously provided by the company.
In 2010, Modi launched an eponymous jewellery business branded NIRAV MODI, in capitals, with the tagline "Haut Diamantaire". New boutiques in Las Vegas and Hawaii have since been added to a stable that stretches from New York to London to Beijing.
He became a man whose diamond necklaces were sold, with his name attached, by Sotheby's. "Pure feminine elegance," says a Hong Kong auction catalogue note of one 85.33 carat diamond necklace.
The auction house posted an online slideshow of jewellery-on-stars at the 2017 Oscars and highlighted supermodel Karlie Kloss having "a major Nirav Modi moment with her diamond 'Mughal' choker."
But the celebrity links could be starting to break.
A spokesperson for Chopra, the film star, said in a statement: "She is currently seeking legal opinion with respect to terminating her contract with the brand in light of allegations of financial fraud against Nirav Modi."