Dean has worked in a number of roles, including professional acting. She is perhaps best known as a former host of Play School, a children's television programme, but has also acted on stage and been a radio announcer. She has also worked in the education sector.
Early in Dean's political career, she served on the Waitaki District Council, representing the Oamaru ward. She also unsuccessfully contested the mayoralty.
In the 2005 election, she was the National Party's successful candidate for the Otago seat, a traditional National stronghold which had unexpectedly been taken by the Labour Party's David Parker. For this election, Dean campaigned on water issues, saying in her maiden speech to parliament that she believed water to be the "single most important issue facing New Zealand today". She was returned to Parliament in 2008 and 2011 for the geographically similar Waitaki electorate. Dean was confirmed as Waitaki's representative in the 2014 election.
Jacqui Dean has been vocal on drug-related issues in New Zealand although she has no official role in this capacity.
Jacqui Dean campaigned for the banning of the sale of "party pills", namely Benzylpiperazine (BZP), over which Associate Health Minister Jim Anderton (Progressive party) has accused her of indulging in political grandstanding, saying – "Perhaps Mrs Dean doesn't subscribe to the idea that any Government must balance the need to act promptly with its responsibilities to act fairly and follow due process, particularly where its actions affect those who are currently acting within existing legal constraints." Dean's press releases refer to BZP as either "cattle drench" or a "worming agent". BZP was developed for this use, but has never been commercially used as a wormer or drench.  Evidence that Dean has used to promote the BZP ban (such as the MRINZ report on BZP) has been criticized as consisting of flawed research which does not meet peer review requirements.
In November 2007 Jacqui Dean called for the government to take action against Salvia divinorum, saying – "Salvia divinorum is a hallucinogenic drug, which has been banned in Australia, and yet here in New Zealand it continues to be sold freely." and "We’re dealing with a dangerous drug here, with the minister's wait and see approach like playing Russian Roulette with young people's lives." In March 2008 she was reportedly pleased on hearing about plans for action against salvia, but saying she was not hopeful it would be fast, given that it had taken the Government two and a-half years to move on BZP. Her concern about salvia was that people were self-medicating with it and combining it with other drugs including alcohol. "I don’t think we understand the long-term effects of Salvia divinorum." she said.
Opponents of prohibitive Salvia restrictions argue that such reactions are largely due to an inherent prejudice and a particular cultural bias rather than any actual balance of evidence, pointing out inconsistencies in attitudes toward other more toxic and addictive drugs such as alcohol and nicotine. While not objecting to some form of regulatory legal control, in particular with regard to the sale to minors or sale of enhanced high-strength extracts, most Salvia proponents otherwise argue against stricter legislation.
When questioned by Maori Party MP Tariana Turia, on why she was unwilling to take the same prohibitory line on smoking cigarettes and drinking alcohol as she took on BZP, Ms Dean said – "Alcohol and tobacco have been with our society for many, many years." It is estimated that alcohol-related conditions account for 3.1% of all male deaths and 1.41% of all female deaths in New Zealand.
Dean's Otago electorate is also home to approximately 5% of New Zealand's wine production, described by the New Zealand Wine Growers Association as a new but aggressively expanding wine area, which is now New Zealand's seventh largest wine region.
In August 2007, as a result of emails from ACT on Campus members based loosely around the well known Dihydrogen monoxide hoax, she sent a letter to Associate Health Minister Jim Anderton, asking if there were any plans to ban "Dihydrogen Monoxide", apparently not realizing that this is water.
In September 2007, the Social Tonics Association of New Zealand (STANZ) called for Jacqui Dean to step down from speaking on drug issues after she demonstrated – "a lack of credibility in calling for the ban of dihydrogen monoxide (water.)" STANZ Chairman Matt Bowden said – "The DHMO hoax played on the member this week is not a joke, it highlights a serious issue at the heart of drug policy making. Ms Dean demonstrated a ‘ban anything moderately harmful’ reflex. This approach is just downright dangerous." – "Jacqui Dean has clearly demonstrated a lack of credibility in her requests to the Minister to consider banning water; She has also seriously embarrassed her National Party colleagues who can no longer have confidence in her petitions to ban BZP or anything else."
When interviewed on the radio by Marcus Lush on 14 September 2007, she referred to the members of ACT on Campus as "left wingers". She also suggested that there were no lessons to be learned from her attempts to call for a ban on water.