Born in Hanford, California, Parnell is a graduate from the University of Puget Sound's School of Law (now known as Seattle University School of Law). He practiced law before being elected to the Alaska House of Representatives in 1992 and he continued to work in private legal practice while he was a member of the Alaska House and later, the Alaska Senate. He served two terms in the Alaska House from 1993 to 1997 before he was elected to one term in the Alaska Senate from 1997 to 2001. Parnell continued his legal career in the private sector, working as an attorney and as the state government relations director for Phillips Petroleum (Alaska) (now known as ConocoPhillips Alaska) and an attorney at the law firm Patton Boggs.
Returning to public service, Parnell won the Republican primary race for lieutenant governor in 2006 and became Sarah Palin's running mate in her 2006 gubernatorial campaign, where the Palin-Parnell ticket defeated former Democratic Governor Tony Knowles. Parnell was sworn in as Lieutenant Governor of Alaska in December 2006 and later assumed the governorship after Palin resigned in July 2009. Parnell was elected to a full term as governor in 2010, defeating former State Representative Ethan Berkowitz in the general election. Parnell is the first unelected Alaska Governor to be elected in his own right. He was narrowly defeated for a second term in 2014 by the "unity ticket" of Republican-turned-Independent Bill Walker and Democrat Byron Mallott.
Sean Parnell was born in Hanford, California, the elder of two sons of Thelma Carol (née Liebherr) and Kevin Patrick "Pat" Parnell. As children, Parnell and his younger brother, Schoen (pronounced "Shane"), were raised in a close-knit family. Two of his paternal great-grandparents were Norwegian.
Sean's father, Pat, was stationed at Fort Richardson, near Anchorage, Alaska, while he served in the U.S. Army during statehood years (1957 - 1959), and returned to Alaska with his family in 1973, establishing residence in Anchorage. Sean Parnell was 10 years old at the time.
Parnell's mother worked as a high school teacher for more than twenty-five years. She taught at Bartlett High School and East Anchorage High School, the latter a short distance from their home. Both of Parnell's parents were entrepreneurs, owning a retail photocopy and office supply business together in Anchorage for more than twenty-five years. Parnell worked in the family business as a teenager and during his college years.
In 1980, Pat Parnell, a Democrat, ran against incumbent Don Young for Alaska's sole seat in the United States House of Representatives, taking 25.82% of the vote.
Parnell graduated from East Anchorage High School in 1980, earned a bachelor's degree in business administration, B.B.A., in 1984 from Pacific Lutheran University, and a juris doctorate (law degree) in 1987 from the University of Puget Sound School of Law (now known as Seattle University School of Law). He is admitted to the bar in both Alaska and Washington D.C.
Parnell married his college sweetheart Sandy in 1987 and the couple returned to Anchorage, where Parnell began practicing law. The Parnells’ daughters, Grace and Rachel, were born and raised in Anchorage, Alaska.
Former First Lady Sandy Parnell became known for her active involvement with the governor in his Choose Respect initiative — a campaign to raise awareness and educate communities around Alaska about domestic violence and sexual assault. As the First Lady, Mrs. Parnell, along with the governor, regularly visited domestic violence shelters and spoke with survivors of abuse and trafficking.
The Parnells' oldest daughter, Grace Adams, is a professional photographer, and Rachel is a university student, pursuing a history degree. The Parnells also have a yellow Labrador dog named Annie, who was known around Juneau as a part of the Parnell family and a frequent greeter of visiting children at the Governor’s House. In November 2014, just after the election, the Parnells became grandparents for the first time when their daughter Grace and son-in-law Austin had their first child, Rowan.
Sean Parnell worked as an attorney in the private sector from 1987 through 2003, between 2005-2006, and again following his tenure as governor, beginning in 2015. For nine years of that time, he owned his own law practice. In the 1990s, he continued in private practice while he served in the Alaska House and the Alaska Senate. When Parnell left the Alaska Senate, he became director of government relations in Alaska for Phillips Petroleum Alaska, which later became ConocoPhillips Alaska. In 2005, he joined the law firm Patton Boggs, where he exclusively practiced law. Patton Boggs represented ExxonMobil in the Exxon Valdez oil spill litigation, though Parnell had no role in that representation or litigation. Parnell left Patton Boggs less than two years later on December 3, 2006.
In October 2015, Parnell and his wife Sandy, moved their residence to Palmer, Alaska, where he returned to working as an attorney in private practice and opened a law firm, specializing in business law, contracts and real estate.
Parnell was first elected to the Alaska House of Representatives, in 1992 at the age of twenty-nine. He represented a district in Anchorage that included at that time, Independence Park, Dimond Blvd., and the Southport/Bayshore ares of Anchorage. After his first year in the State House, Parnell was named the "Most Effective Freshman Legislator" by his colleagues and those who worked in the State Capitol. This recognition arose because Parnell was known for taking the time to help other legislators hone and pass their legislation and in doing so, learned the legislative process and developed relationships with his colleagues. In 1994, Parnell was re-elected to represent South Anchorage in the Alaska House. Throughout his four years in the Alaska House of Representatives, Parnell was known for his work on the House Finance Committee and in the fight against domestic violence and sexual assault in Alaska. During those years he sponsored and passed seminal legislation known as the Domestic Violence Prevention Act of 1996 that was Alaska’s first consistent, comprehensive statewide policy on this issue.
In 1996, Parnell ran for and was elected to a seat in the Alaska Senate and became a member of the Energy Council and served on the powerful Senate Finance Committee. In 1999 and 2000, he became a member of the Senate Republican Majority's Leadership when his Senate colleagues chose him to serve as the co-chair of the Senate Finance Committee.
In 2000, Parnell finished his first and only term in the State Senate, choosing not to seek re-election. He cited his commitment to his family as his reason and returned to work in the private sector.
Six years later, in 2006, Parnell was elected Lieutenant Governor of Alaska, along with Alaska Governor Sarah Palin. In July 2009, when Governor Palin resigned her position, Parnell became Governor and finished the term of office. In 2010, Parnell won a four-year term as governor in his own right.
In 2005, Parnell ran and won in the Republican primary to become lieutenant governor. Afterward, in the general election, he was paired with Sarah Palin as her running mate. In Alaska, the lieutenant governor candidates run separately from the governor candidates in the primary election race, but after the primaries, the nominees for governor and lieutenant governor run together as a slate. Palin and Parnell were elected with 48.33% of the vote over former Governor Tony Knowles and State Representative Ethan Berkowitz's 40.97% share of the vote.
On March 14, 2008, Parnell began his campaign to take on embattled 18-term member of Congress Don Young in the August 26 Republican primary.
Parnell was endorsed by Sarah Palin, National Review magazine, and the fiscally conservative 501(c)4 organization Club for Growth.
On July 31, 2008, Parnell told Roll Call he would not drop out of his race against Young to run against Senator Ted Stevens, who had been indicted.
Parnell lost the primary for the U.S. House seat. The margin between incumbent Young and Parnell was narrow, and the winner was not immediately clear. The result released on September 18 showed Young winning by 304 votes. Parnell said he trusted the integrity of the work of the Division of Elections, an agency he oversaw as Alaska's lieutenant governor. He said in a statement, "While a recount could change the outcome of this exceedingly close election -- normal human error being what it is -- such a result is unlikely. As such, I do not believe it justifies an expenditure of taxpayer funds."
On July 26, 2009, halfway through her term as governor, Palin resigned. Parnell replaced her becoming Alaska's tenth governor in accordance with the Alaska Constitution. Craig Campbell, commissioner of Alaska's Department of Military and Veterans Affairs, succeeded Parnell as lieutenant governor after Palin first named Joe Schmidt, commissioner of corrections as a replacement for Parnell and Schmidt resigned from the second-in-line position on July 6, 2009.
Parnell ran for a full term as governor in 2010. In the primary, he faced off against Bill Walker, a former mayor of Valdez, Alaska and aide to former governor Walter J. Hickel, and Ralph Samuels, a retiring member of the Alaska House of Representatives. Although Walker seemed to gain traction towards the end based on the issue of building a natural gas pipeline, Samuels and Walker split the anti-Parnell vote and Parnell won the nomination. He and Mead Treadwell, who had won the August primary for lieutenant governor, faced off against the Democratic ticket of former House majority leader and 2008 congressional nominee Ethan Berkowitz and Diane Benson. Parnell-Treadwell eventually defeated Berkowitz-Benson by over ten points.
Parnell ran for reelection in 2014. Former Republican Bill Walker challenged Parnell as an independent politician, and merged his campaign with Democratic Party gubernatorial nominee Byron Mallott, who became Walker's running mate as an independent. He conceded the election to Bill Walker on November 15, 2014.
Parnell drew criticism during his reelection campaign over his support of billions in tax reductions for the petrochemical industry as well scandals regarding accusations of coverups of sexual abuse scandals, cronyism, corruption and whistleblower suppression, within the Alaska National Guard.
Out of 19 Republican governors, Parnell and Pennsylvania's Tom Corbett were the only ones who lost the 2014 elections.