That represented a "massive" 39% increase on the same period last year, according to the latest Mobile Payments Index (MPI) compiled by Adyen, the payments technology company.
Adyen's MPI tracked quarterly mobile payment data from internet-based transactions across its global customer base of 3,500 businesses and it found significant rises in activity across the world.
The UK continued to lead the way with 44.4% of online payments coming from mobile, up from 36.9% a year earlier, and smartphones accounted for two-thirds (66%) of all mobile payments in the country.
"The UK's position as the world's number one in mobile payments speaks volumes for the country's payments infrastructure, its highly competitive mobile network landscape and the general population's continued willingness to exploit new payment channels," noted Myles Dawson, UK country manager at Adyen.
But the US also showed "impressive growth" over the quarter, the report said, with 26.7% of online payments being made on mobile, representing an increase of nearly five percentage points over the past six months.
There was a higher proportion of mobile payments made in Europe (28.6%), but growth over the same period was slower in the region at just two percentage points. Meanwhile, Asia broke the 20% threshold for the first time in the quarter.
The MPI also revealed that tablets may be approaching market saturation because the gap between spending on smartphones and tablets widened "dramatically".
Smartphones accounted for 10.9% of online transactions in March 2014, compared with 9.3% for tablets. But by March 2015, smartphones accounted for 16% of online transactions with tablets at 11.5%.
In terms of operating system, Apple was way ahead with 65% market share of online mobile payments in the first quarter.
But this was down from 69.5% last year as Android increased its market share to 34.9%, up from 30.3% a year ago.
Data sourced from Adyen; additional content by Warc