Sabah maintains autonomy on immigration rules, mostly so that non-Sabahans cannot freely immigrate and swamp the state. Malaysians from Peninsular Malaysia and neighbouring Sarawak are subjected to some level of immigration control, such as showing their identity cards, and are restricted to a stay of 90 days at a time. Foreigners need to fill out a second immigration form. Nevertheless, for most travellers this is just a formality and an interesting extra stamp in their passport. See Malaysia | Get in for details.
By ship
You can enter Sabah by boat from the Malaysian Federal Territory of Labuan, Zamboanga in the southern Philippine, and from Nunukan in East Kalimantan, Indonesia. However, there are no passenger boat services between Sabah and Peninsular Malaysia.
To/from Labuan:
Passenger boats depart Labuan for Kota Kinabalu and Sipitang while vehicular ferries operate between Labuan and Menumbok in the southern part of Sabah. See the individual city pages for ferry details. Labuan is where you have to change boats if you hope to travel between Brunei and Kota Kinabalu. See the Kota Kinabalu to Brunei in a day page tails.To/from Zamboanga:
Boats run between Zamboanga in Mindanao in the Philippines and Sandakan.To/from Nunukan:
At least one ferry daily between Nunukan in East Kalimantan and Tawau.
By plane
Kota Kinabalu International Airport (http://en.wikipedia.org/w...) IATA: BKI ICAO: WBKK is now a major air hub for the Borneo states of Malaysia. The main airlines are Malaysia Airlines (http://www.malaysiaairlin...) and AirAsia (http://www.airasia.com/) providing the main links with Peninsular Malaysia, Sarawak and as several regional destinations like Clark in Angeles City 80km north of Manila, Bangkok, Singapore, Hong Kong, Guangzhou, Kaohsiung, Taipei, Seoul, Tokyo, Osaka and Macau. Other airlines which service Kota Kinabalu are Dragonair (http://www.dragonair.com/) between KK and Hong Kong, Silkair (http://www.silkair.com/) Singapore, Royal Brunei Airlines (http://www.bruneiair.com) Bandar Seri Begawan and Asiana (http://www.asiana.co.kr/e...) Seoul. Malaysia Airlines subsidiary MASWings (http://www.maswings.com.my) provides the rural air service links with several minor airports in Sarawak as well as within Sabah. The airport has two terminals - the main one for full fare flights, and a second terminal for budget carriers like AirAsia. For flight details and how to get to the airport terminals, see Kota Kinabalu's "Get in" section.
There are also direct flights from Kuala Lumpur to Sandakan Airport and Tawau Airport.
By road
The only place where you can travel overland into Sabah is from Sarawak through the border crossing at Merapok near Lawas. Those who are not citizens of Sabah or Sarawak will have to go through immigration checks here. The road between Kota Kinabalu and the border is sealed all the way and in good condition. If you are planning to do the overland trail from Sarawak to Sabah, it is possible to get from Bandar Seri Begawan in Brunei - or with a bit of a stretch, from Miri - to Kota Kinabalu within a day. See Kota Kinabalu to Brunei in a day for details.
There is no official land crossing with Indonesia, although there may be some informal tracks from the interior of Sabah which locals use to get to East Kalimantan.