Taiwan Mobile plans a soft launch of third-generation (3G) services later this month, ahead of a full-scale roll-out planned for later this year.
The company's foray into high-speed data services will be watched closely by industry analysts.
In addition to offering video content to lure subscribers, Taiwan Mobile should be able to price its voice services at a steep discount to 2G operators.
Taiwan Mobile has 6.63 million subscribers, compared with 8.1 million claimed by state-run Chunghwa Telecom.
Sources told the South China Morning Post 3G services would be launched on or around May 25 but with no fanfare or official announcement.
Instead, high-value customers will be invited to sign up for 3G while walk-in customers will be given the opportunity to buy a handset and sign up.
The soft launch will allow Taiwan Mobile to work out any bugs before a full-scale launch later this year.