In 2010, Brown faced Democratic candidate Massachusetts Attorney General Martha Coakley in a special election which occurred after the 2009 death of longtime Senator Ted Kennedy.

While initially trailing Coakley by a large margin, Brown saw a sudden late surge and posted a come-from-behind win to become the first Republican elected to the U.S. Senate from Massachusetts since Edward Brooke in 1972.

After two weeks on a crash diet of "three cans of tuna a day" and intensive workouts[20] he was featured in the magazine's centerfold, posing nude but strategically positioned so that according to Brown, "You don't see anything".

The Cosmopolitan appearance and its $1,000 fee[26][32][33] helped pay for law school, and began for Brown a "long, lucrative" part-time catalog and print modeling career in New York and Boston during the 1980s.

In the Massachusetts Senate, Brown served on committees dealing with consumer protection, professional licensing, education, election laws, public safety, and veterans' affairs.

[24] In February 2007, a controversy arose after Brown's appearance at King Philip Regional High School in Wrentham, Massachusetts as part of a debate on gay marriage.

[41] In January 2010, The Boston Globe reported that during six terms in the Legislature, three each in the House and Senate, Brown had a modest record of legislative initiatives, but he had carved out a niche as a leading advocate for veterans.

Richard Tisei of Wakefield, Massachusetts, the leader of the Republican minority in the state Senate, called Brown "the acknowledged expert on veterans' issues".

"[42] Brown lists among his achievements as a legislator his authorship of a 2007 law that created a check-off box on state income tax forms for veterans to indicate whether they served in Iraq or Afghanistan.

The state uses the information to notify veterans of available services and benefits, including the Welcome Home Bonus[43] that provides $1,000 for those returning from active duty in Afghanistan or Iraq.

[47] Boris Shor, political scientist at the Harris School of Public Policy, described Brown as a liberal Republican by national standards, but well-suited for his Massachusetts constituency.

At the outset, he faced overwhelming odds because he was relatively unknown compared to Coakley, he was running as a Republican in a very Democratic state, and much of his campaigning had to be done during the Christmas and New Year's season when citizens do not generally pay much attention to politics.

[57] This amendment would have allowed individual healthcare workers and hospitals to refuse to provide emergency contraceptive care (the morning-after pill[58]) to rape victims if they objected due to a religious belief.

[59] Brown's daughter Ayla called the Coakley ad "completely inaccurate and misleading", and stated that her father would never deny care to a rape victim.

The Rothenberg Political Report released a statement that "the combination of public and private survey research and anecdotal information now strongly suggests that Republican Scott Brown will defeat Democrat Martha Coakley in tomorrow's race.

[84][additional citation(s) needed] In December 2013, he sold his primary home in Massachusetts and expressed to the Rye town clerk "his intention to establish residency and register to vote".

55% of those polled had favorable opinions of Brown nearly five months after his January 19, 2010, special election victory to finish the term of the late Senator Edward Kennedy.

[99] On March 30, 2011, the Democratic Senate Campaign Committee released a poll showing that Brown remained the "most popular politician in the Commonwealth of Massachusetts, with an approval rating of 73 percent."

[112] In early February 2014, Brown's email list was used to promote "a video from a doctor warning against flu vaccines, fluoridated water, and excessive exercising, among other questionable medical claims.

[118] In 2015, Brown used his Facebook page to promote AdvoCare, a company that uses multi-level marketing to sell nutrition, weight-loss, energy, and sports performance products.

Brown criticized the bill for including a provision much like the Troubled Asset Relief Program, stating: "Banks making lending decisions with government funds is not the way to get our economy moving again.

[156] In 2007, Brown wrote a law establishing a check off box on State income tax forms to allow a filer to indicate if he or she is a veteran of the Iraq or Afghanistan wars.

[158] Brown voted for a state measure on patients' rights that, among other provisions, requires emergency rooms to provide what is known as the morning-after pill[58] to rape victims to prevent an unwanted pregnancy from developing.

[160][161] Brown supports expanding solar, wind, and nuclear power, and offshore drilling exploration as a means to reduce the country's dependence on foreign oil.

[166] The bill was verbally supported by President Barack Obama during his third State of the Union address, and passed a major procedural hurdle in the Senate by a vote of 93–2 on January 30, 2012.

[189] After the resolution passed unanimously, Brown noted to the LA Times that this "cannot undo the hurt caused by past discrimination against Chinese immigrants, but it is important that we acknowledge the wrongs that were committed many years ago".

When asked about same-sex marriage, he focused on the economy; "Brown said the economic challenges in regards to jobs, healthcare and college tuition affect both straight and gay couples and that is what he is working to address.

Brown was awarded the Army Commendation Medal for meritorious service in organizing the National Guard to quickly support homeland security following the terrorist attacks of September 11, 2001.

[22] Brown has received the Public Servant of the Year Award from the United Chamber of Commerce for his leadership in reforming the state's sex offender laws and protecting victims' rights.

The Brown family has "assisted efforts to raise $5.5 million" to replace the abbey's candy factory with a new greener facility with solar panels and a wind turbine.