NTT Docomo's reputation for reliability is under pressure after it handed subscriber data to Amazon Japan without consent, suffered a nationwide outage lasting about 14 hours and reported a breach of up to 300,000 customer records.
The internal affairs ministry issued the carrier administrative guidance in writing under the Telecommunications Business Act on November 6, 2026. The ministry acted over the transfer of phone numbers and rate-plan details for 344,213 subscribers, including users of the Docomo MAX plan.
Docomo had set up a system to obtain consent at sign-up for information sharing tied to an Amazon Prime discount. In February 2026 a staff member changed the online application screen and, by mistake, deleted the consent item. The data was shared without permission from April 21 to August 20.
The information was not used by Amazon and has been deleted, according to the company. Docomo has long been the industry's dominant carrier, and the run of problems has fed distrust among users.
Users question the silence
According to reports, Docomo learned of the problem on August 18, 2026, but did not notify users until September 15. Complaints online focused on the gap and on the company's public response.
“Why was there a whole month between finding out and telling us?”a social media user
“They're trying to settle it with an apology, but in Europe or the US this would be a much bigger problem.”a social media user
“No explanation on the official site...”a social media user
“I want them to be more honest with users.”a social media user
Two failures in a week
On November 5, 2026, a nationwide outage hit Docomo's newest 5G SA service, affecting up to about 1.587 million lines. Voice calls, data and SMS were hard to use from around 11:18 a.m. until about 1:20 a.m. the next day, roughly 14 hours.
The cause was a concentration of processing at a switching system, and Docomo said it found no sign of a cyberattack. Ordinary 5G and 4G users and emergency calls were unaffected.
The same day, Docomo said unauthorized external access had leaked customer data on up to about 300,000 people. The records included names, addresses and phone numbers, plus identity document numbers and bank account details for some users. Docomo detected the access on November 4 and halted procedures on My Docomo and its online shop early on November 5, but could not stop the leak.
According to reports, president Yoshiaki Maeda apologized at a news conference on November 6 and said the company would consider compensation payments to those affected.
A missed quake alert
On October 16, 2026, an Earthquake Early Warning issued by the Japan Meteorological Agency for a quake near the Kamchatka Peninsula did not reach Docomo users through Area Mail, the carrier's alert service. Rivals delivered it, but Docomo's system could not read a data format that differed in part from the usual one. The warning was later withdrawn.
Maeda expressed regret over the failure at an earnings briefing on November 4, according to reports. The outage, the breach and the ministry's guidance followed in quick succession.
Users have often complained that Docomo's network is hard to connect to. The lapses now extend to how the company manages customer data, secures its systems and explains problems when they occur.
Docomo suffered another large 5G SA outage on November 11, 2026. With failures coming this often, scrutiny is turning to how the organization is run, and to whether the carrier once known for reliability can earn it back.