The HSBC Emerging Markets Index (EMI), a monthly indicator derived from Purchasing Managers' Index surveys, stood at 52.3 in June, up from 50.6 in May, signalling the sharpest rate of expansion since March 2013.
The pick-up in output growth was reflected in both manufacturing and services, most notably the latter, where activity expansion hit a 15-month high, HSBC said.
Stronger output growth was registered across global emerging markets in June, primarily driven by India and China.
China posted the sharpest increase in output for 15 months, while India saw the steepest expansion since February 2013. Russian private sector output stabilised and Brazil, however, registered a further flat trend in activity.
During June, the HSBC composite index for India, which maps both manufacturing and services, stood at 53.8, whereas for China it was 52.4, Brazil (49.9) and Russia (50.1). An index measure of above 50 indicates expansion.
"Emerging markets showed new signs of life in June after stagnating in prior months, enjoying the strongest upturn in business activity since the end of the first quarter of last year," Markit Chief Economist Chris Williamson said.
Williamson added that "at present, the developed world is driving global economic growth, but the emerging markets are now at least showing signs of exerting less of a drag. If momentum can build in coming months, improvements in the emerging markets will help lift global growth higher in the second half of 2014."
Inflationary pressures remained subdued in June, as despite input price inflation reaching a four-month high, prices charged for finished goods and services continued to rise only fractionally.
Meanwhile, the HSBC Emerging Markets Future Output Index that tracks firms' expectations for activity over the next 12 months, rose for the first time since February, indicating strengthening sentiment across emerging markets.
India registered the brightest outlook for the next 12 months for the third successive month, ahead of Brazil and China, respectively.