The consultancy surveyed 5627 respondents from 22 countries for the study, which found that convenience is edging out consumer concerns over privacy and security.
Compared with only 18 months ago, the global percentage of respondents who have used their mobile device for banking has more than doubled from 19% to 46%, while the percentage that have used it to buy goods and services has risen from 10% to 28%.
This surge is being led by the world's fastest-developing economies. In China, 77% of respondents say they have used their mobiles for banking and 44% for retail transactions, while in India 38% are using them to shop, and 43% for financial business.
Asia-Pacific consumers are much more likely to be heavy users of mobile online services than those in Western Europe and the US, says KPMG.
Only 19% of US consumers have conducted banking transactions on a mobile device, the study finds, although this is is more than double the numbers counted 18 months ago.
Among naysayers, 52% cited security and privacy as the primary reason.
Lack of availability may also be a major inhibitor. Nearly three-quarters of US respondents said that their current bank either does not offer banking through a mobile device or that they did not know if their bank offered this service.
Carl Carande, a principal in KPMG banking and finance advisory practice, says: "To continue to spur adoption, banks may need to continue to educate consumers about the security of the mobile banking environment and further promote the availability of this vehicle that helps make banking more accessible and convenient."