Geographic (fixed line) telephone numbers consists of an area code of 1 to 2 digits (excluding the leading zero) followed by a 6 to 8-digit subscriber number. Mobile phone numbers consists of a mobile phone code of 2 digits followed by a 7 to 8-digit subscriber number. Mobile phone codes are originally assigned to specific mobile network operators, however with mobile number portability , a mobile phone number might not be longer associated with its original assigned operator.

Calls to Singapore do not require international dialing; calls are made using the 02 access code. Similarly, calls to Brunei from East Malaysia can be made using the 080 access code but calls from Peninsular Malaysia to Brunei require the international prefix 00673.

Geographic (fixed line) area codes are, excluding the STD prefix 0, one digit in Peninsular Malaysia (area codes 3 to 7 and 9) and two digits in East Malaysia (area codes 8x). In Peninsular Malaysia, an area code is usually shared by multiple states and territories and roughly follows state borders. The two East Malaysian states, Sabah and Sarawak , are split into multiple area codes.

Fixed line subscriber numbers are seven digits in Peninsular Malaysia (except Selangor , Kuala Lumpur and Putrajaya , i.e. area code 3) and six digits in East Malaysia. Prior to 2001, subscriber numbers were seven digits in Kuala Lumpur, Putrajaya and Selangor. From 1999 to 2001, subscriber numbers in these areas were gradually expanded to eight digits in phases to meet new demands that resulted from the growing population in Klang Valley

Thus, a full national number is 10 digits in area code 3 and 9 digits elsewhere, including the STD prefix 0. When writing a telephone number with the area code, the area code and subscriber number is separated with a hyphen. Examples:

Malaysia employs an open dialing plan , which means calling within the area code does not require the area code to be dialed, apart from mobile phone calls. Calls to and from mobile phones requires full national dialing. e.g. When calling a number 2xxx xxxx in Kuala Lumpur (03) from a fixed line phone:

Mobile phone codes and IP telephony codes are in the area code 1, ranging 2 digits excluding the leading zero.

Originally, each mobile phone operator is issued one mobile phone code. Through a series of mergers, there are currently three major mobile phone operators: Celcom , Maxis and DiGi . In 2005, as existing numbers begin to run out, the three mobile phone operators are assigned numbers in 014 code distinguished by the first digit of the subscriber number.

A mobile phone number consist of a three-digit mobile phone code and a seven-digit subscriber number. Therefore, a mobile phone number is officially written as 01x-xxxxxxx, but for unofficial usage (such as number exchanging) are usually written as xxxxxxxx For example number 015-5123456 are written as 55123456. Calling from mobile phones to fixed lines and vice versa requires full national dialing. Since 2009 calls between mobile require the full national number, regardless if both parties are in the same mobile phone code (i.e. 012 to 012). Calling from outside Malaysia requires the leading zero to be dropped.

Mobile phones in Malaysia uses 900/1800 MHz for GSM and 2100 MHz for WCDMA. Domestic roaming service is available free within Malaysia in places where there is only a single transmitter in place due to restrictions.

As codes are being exhausted, two new ranges 011 and 015 is made available for assignment. Subscriber numbers will be eight digits long, resulting in an 11-digit mobile number including the leading zero. The two major ISPs in Malaysia, TMNet and Jaring are assigned numbers in the 015-4 prefix to provide VoIP (also known as Telephony Service over IP, TSoIP) service.

Starting 15 December 2010, the prefix 011-1 followed by 7 digits would be available for use, which marks the first availability where a full cellular number contains 11 digits.

Jaring MIMOS won bids for 3G services, but had yet to use up a prefix. U Mobile (formerly MiTV), part of Berjaya Holdings , too won a 3G-only license and thus used the 018 prefix with 7 numbers. Celcom also offers satellite calls system, thus offering 99.99% coverage in outdoor areas in Malaysia using Vodafone backbones.

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Recently, the MCMC announced the mobile number portability (MNP) service for mobile carriers. Thus, subscribers are allowed to retain their mobile numbers when they switch to another service provider, in a bid to increase market competition. Therefore, the mobile number prefix only indicates the original service provider.

Number portability has not been offered for fixed lines, as TM holds a monopoly except in Putrajaya and some areas in the Klang Valley .