Goldsworthy was elected to the House of Commons at the 2005 General Election for Falmouth and Camborne when she defeated the sitting Labour MP Candy Atherton. She gained the seat with a majority of 1,886 and made her maiden speech on 19 May 2005. She names former Cornish Liberal MP David Penhaligon as her greatest hero. Her election in 2005 meant that the Liberal Democrats held all the Westminster Parliament seats in Cornwall, for the first time since 1923. In 2005, she was appointed as a spokesperson on health by Charles Kennedy, and promoted in 2006 by new leader Sir Menzies Campbell as Vince Cable's deputy in the Treasury team. She was also member of the Public Administration Select Committee from 2005 until mid-2006. Julia Goldsworthy was promoted again in December 2007 to become the Liberal Democrat shadow secretary on Communities and Local Government. As an MP, she worked on issues such as the 'Axe the Tax' campaign against council tax, pensions, student tuition fees, health funding formulas and the abolition of central housing targets on local communities. During her parliamentary career, Goldsworthy also used the social networking websiteFacebook as a way of gauging the opinions and views of her constituents, and this has led her to campaign for various issues. On 14 May 2008 in the House of Commons debates, she presented a petition on behalf of many thousands of people living in Cornwall who would like to see Cornwall be recognised as a network region on the website. Goldsworthy is a supporter of the Facebook Cornish Tickbox for the 2011 Census campaign. Goldsworthy co-sponsored the Sustainable Communities Act 2007 Act 2010.
Expenses
The Daily Telegraph showed that in 2006 Goldsworthy bought a "£999 television, £1,500 of furniture in House of Fraser, a £1,111 sofa bed and a £1,200 rocking chair from Heal’s, an upmarket furniture store", as part of moving into an unfurnished flat, but she did not claim the full amount for these items. Between 2005 and 2008, she also regularly claimed £400 per month for food, as many other MPs did at the time, without providing receipts to prove the expenditure. She has responded with a full account of her transactions and a statement that she opposed steps to block the publication of MPs' expenses claims. In February 2010, it was again reported that she repaid £1,005 for the "designer pink rocking chair" and £171.32 over-claimed in mortgage interest in 2005–06.
2010 and 2015 elections
At the 2010 general election, Goldsworthy stood at the new seat of Camborne and Redruth which she narrowly lost by just 66 votes to the Conservative candidate George Eustice. Following her defeat at the 2010 general election, she was named special adviser to Chief Secretary to the TreasuryDanny Alexander. Five years later she contested the seat again. However, on this occasion, Goldsworthy finished in fourth place with 5,687 votes. Eustice retained the seat with 18,452 votes to 11,448 to Labour, with UKIP finishing in third place.