She made her political debut in the 2011 general election as part of a four-member PAP team contesting in Holland–Bukit Timah GRC, and won 60.1% of the vote.
From 1998 to 2000, she was Assistant Director for Finance Policy and Planning at the Ministry of Health (MOH). From 2000 to 2003, she was Assistant Director for Implementation Planning at the Ministry of Home Affairs (MHA). From 2003 to 2006, she was Deputy Director for Trade at the Ministry of Trade and Industry (MTI).
From 2007 to 2009, Sim was seconded to the International Enterprise Singapore as its Regional Director based in Shanghai, where she headed a team assisting Singapore-based companies with investment and sales in East China.
From 2009 to 2011, she was Director of the National Population Secretariat and led efforts to restructure the secretariat into the National Population and Talent Division under the Prime Minister's Office (PMO).
The party affiliation of each member is indicated right after the constituency/seat he or she represents. PAP: People's Action Party; WP: The Workers' Party; PSP: Progress Singapore Party All of the leaders of the respective GRCs are in underline. MP(s) who is go on a leave of absence is in italic. NMPs do not belong to any party.
The party affiliation of each member is indicated right after the constituency he or she represents. PAP: People's Action Party; WP: The Workers' Party NMPs do not belong to any party. There were two terms of NMPs in this parliament, with nine NMPs in each term.
The party affiliation of each member is indicated right after the constituency he or she represents. PAP: People's Action Party; SPP: Singapore People's Party; WP: The Workers' Party For NCMPs, Gerald Giam and Yee Jenn Jong are from the WP, while Lina Loh is from the SPP. NMPs do not belong to any party. There were two terms of NMPs in this parliament, with nine NMPs in each term.