In 2002, Tan represented Malaysia in the 2002 Miss Global Petite World Finals in Montreal where she won Second Runner Up and the “Miss Congeniality” subsidiary title. In 2006, she was voted by FHM as Malaysia’s sexiest woman.
On Tan's debut music album, Crossing Bridges, she collaborated with composers/writers Jorgen Elofsson, Phil Thornalley, Andrew Fromm and Chris Rojas. The album also contained three songs Tan personally wrote and composed. In 2007, she appeared on the Live Earth stage at Live and Loud KL 2007 before acts such as Elliott Yamin, Shaggy and Whitney Houston.
In February 2009, Hannah released her first Malay song, which she had composed herself in English, "Indah."
Her Malaysian single "Angel" was released on Valentine's Day 2010, with 20% of the sales donated to an orphanage in Kuala Lumpur. The single was the first from a new album to be released at the end of 2010.
In October 2009 she became the first Malaysian to venture into the commercial Japanese entertainment scene with the signing of a multi-million dollar recording contract to Tokyo-based Fillmore Far East Inc group. Her 2-year contract will see the release of a Japanese debut Single in August 2010.
In January 2008, she made her debut into the Malay entertainment scene by playing the lead role in the Malay tele-movie Bezanya Cinta.
Hannah was invited in October 2008 by film director Afdlin Shauki to play the lead female role as an undercover interpol agent in his My Spy
At the same time, her 2009 I’ll Be Home For Christmas Christmas saw the largest gift collection in a day for the underprivileged children in local orphanages around the Klang Valley, totaling up to more than 650 gifts worth over RM15,000. For the concert, Hannah invited friends from the industry to perform and be part of the community service event.
Sony Pictures appointed Hannah as the first ambassador for Animax Asia in November 2007.