Though Jassy gave no breakdown, the announcement follows Amazon's cloud computing unit Amazon Web Services (AWS) saying last month it will invest 1.06 trillion rupees ($12.9 billion) in the country by the end of 2030.
Earlier, Amazon had announced a $6.5 billion investment plan, largely to boost its e-commerce business where it competes with Walmart's Flipkart and billionaire Mukesh Ambani's Reliance Retail.
The new investment amount committed now comes to around an additional $6.5 billion.
The e-commerce giant's announced investment during Modi's trip adds to other companies, including U.S. semiconductor toolmaker Applied Materials and memory chip firm Micron Technology, which have made commitments during the Indian prime minister's state visit.
Modi and Jassy spoke about supporting Indian startups, creating jobs, enabling exports, digitisation, and empowering individuals and small businesses to compete globally, an Amazon blog post said.
Separately, Google GOOGL.O will open a global fintech operation center in GIFT City in India's western state of Gujarat, with teams working on operations supporting its payment service GPay, and other product operations at Google, the company said in a statement to Reuters.
"We shared Google is investing $10 billion in the India digitisation fund, and we are continuing to invest through that," CEO Sundar Pichai told reporters in a video shared on Twitter by Reuters partner ANI company.
On the final day of his Washington trip, Modi met with U.S. and Indian technology executives, including Apple's AAPL.O Tim Cook, Google's Pichai and Microsoft's MSFT.O Satya Nadella and appealed to global companies to "Make in India".
