Of the transactions, 80% were conducted on M-Pesa, the platform run by Kenya's biggest mobile operator Safaricom, which is 35% owned by South Africa's Vodacom.
The Communication Authority has in the past said such transactions included those related to loans, savings and cross-border transfers, as well as payments for utility bills and other goods and services.
The data showed Safaricom's market share had slipped to 63.5% in the three-month period from 65.4% a year earlier. The company had 33.1 million subscribers at the end of June, up from 29.7 million subscribers in June 2018, it showed.
The regulator said the market share of Airtel, Safaricom's closest competitor, was 24.6% during the quarter, up from 21.4%.
India's Bharti Airtel said in February its Kenyan unit had agreed to buy Telkom Kenya, another operator, to create a stronger challenger to Safaricom. But the merger was halted in August pending a corruption probe.
The number of active SIM cards in Kenya stood at 52.2 million at the end of June, up from 45.5 million a year earlier, the regulator said.
($1 = 103.7000 Kenyan shillings)