We often get asked about cell phone service in Japan or more specifically get e-mails like this:
"Hi! I'm an American and will be traveling to Japan this
spring to teach in Japan, will my cell phone work over there?"
Click here for more information on renting a cellphone that works in Japan.
The short and long of it is probably not and here's why...
The U.S. standard for GSM and the standard that Japan's big makers that Softbank, NTT, Docomo, KDDI use aren't compatible. What this means is that your cell phone might work fine if it is 3G and won't work at all or may have impaired functioning e.g. some menu items will work and others won't if it isn't 3G.)
The Bottom Line
The bottom line is that your phone must be a 3G or W-CDMA type to face any chance of working in Japan. And probably the only way you'll know for sure if it will work is to call your service provider. There are workarounds however...
Buy a Cell Phone Before You Go to Japan
So at this point you have a couple options. One. Buy a phone designed to work in Japan with a SIM card before you arrive in Japan. Which is pretty hassle free, rates are good all you need is a credit card and a mailing address. You won't need to provide various forms of I.D. and won't have to deal with long contracts etc.
Frequency Compatibility is the Problem
Basically, it's a frequency compatibility problem and here's the nitty-gritty of it: most GSM phones sold in the US are only compatible with the nation-wide operating frequency of 1900 MHz (or the emerging 850MHz band). Overseas services use 900 and/or 1800 MHz frequency standards. (There isn't a GSM network in Japan so therein lies the problem in using U.S. produced phones.)
Cell Phone Service in Japan & Other Workarounds
Another option is just wait until you arrive in Japan and buy one directly from one of the many shops in Japan. Be aware of a few points before you decide to buy one in Japan. Firstly most Japanese phones are bundled.. What this means is that when you buy the phone you also get to buy a 2 year contract or service agreement with it. (Bummer...I know.)
If you are a foreigner they will require documentation in order to issue the phone. This usually means a "gaijin card" and or passport. Sometimes even proof of a bank account. One work around is to have a Japanese national take care of the paperwork then again that same national is also ultimately responsible for bills you incur and don't pay.