Lim served at Singapore's National Computer Board as Chief Executive from 1986 to 1991, and as Chairman from 1994 to 1998. He also served at the Economic Development Board (EDB) as Deputy Managing Director based in New York City from 1991 to 1993, and as Managing Director from 1994 to 1996.
At the 1997 general election, Lim was a PAP candidate in the Tanjong Pagar Group Representation Constituency (Tanjong Pagar GRC), which was led by the late Mr Lee Kuan Yew (who died in 2015) and was elected in a walkover. He was on the PAP's team in Holland-Bukit Panjang GRC at the 2001 general election, and in Holland-Bukit Timah GRC at the 2006 general election, and was elected unopposed on both occasions. At the 2011 general election, Lim stood in East Coast GRC, where the PAP's team defeated the team from the opposition Workers' Party by 59,992 votes (54.8%) to 49,429 (45.2%).
Lim served as Deputy Secretary-General of the National Trades Union Congress (NTUC) from 1997 to 1999. He also served on the Committee on Singapore's Competitiveness from 1997 to 1998, and chaired its Sub-committee on Manpower Development.
In 1999, Lim was appointed a Minister of State at the Ministry of Trade and Industry and the Ministry of Information, Communications and the Arts.
Lim was made the Acting Minister for the Environment in 2000. He became a full member of the Cabinet in 2001.