The free service would be limited to 200 megabytes of high-speed data per month -enough to upload about 800 Instagram photos or listen to more than three hours of streaming music, the company said.
T-Mobile US Inc. said the free service comes with no obligations, but the company expects people will want to buy plans for additional data once they grow accustomed to having it.
People typically buy tablet computers that access the Internet using Wi-Fi only. Models with 4G LTE cellular access typically cost $100 to $130 more, but T-Mobile marketing chief Mike Sievert said many people are reluctant to purchase cellular-enabled tablets for fear they would be stuck with monthly data service costs.
By guaranteeing free data service, he said, T-Mobile is hoping to encourage people to buy LTE tablets.
The latest offer, announced Wednesday, comes as the company tries to shatter longstanding industry practices and brand itself as the Un-Carrier.
In March, the company dropped conventional two-year service contracts in favor of selling phones with installment plans. In July, it introduced a program that lets people upgrade phones more frequently - up to twice a year. This month, the company eliminated data and texting fees in more than 100 countries and capped charges for international voice calls.
There are signs the efforts are working. In the April-June quarter, T-Mobile gained long-term, good-credit customers for the first time in at least two and a half years. T-Mobile added a net 688,000 such customers in the quarter, compared with a loss of 557,000 in the same period a year earlier.
The net increase includes 3,000, or less than 0.5 percent, for non-phone service such as tablets. T-Mobile officials believe there's room for further growth.
All tablet computers, including Apple's iPad, Google's Nexus 7 and Amazon's Kindle Fire, are eligible for the offer as long as they work on T-Mobile's network. Sievert said most tablets do.
The new iPads announced Tuesday are universal models, meaning they will work on various LTE networks around the world. Previously, Apple sold separate models compatible with a subset of networks.
Tablet owners will need to buy a SIM card that costs about $10.
T-Mobile said it will sell iPads under installment plans, but people who buy tablets elsewhere will qualify as well.
The free access is limited to the United States.
For $10 a month, T-Mobile phone customers can buy an additional 500 megabytes of high-speed data in the U.S. and unlimited data at slower speeds. That plan also comes with unlimited data at the slower speeds in more than 100 countries. Non-phone customers can pay $20 a month for the same plan. There's no contract, so people can sign up for a month at a time. There are also daily and weekly options.
At rival AT&T, monthly plans start at $15 for 250 megabytes. The company recently introduced $5 day passes, which it says is ideal for travelers looking for an alternative to Wi-Fi hotspots.