He played youth football and ran track in Pensacola, Florida, with future NFL running back Alfred Morris.

[8][9] He signed with the Seattle Seahawks as an undrafted free agent following the end of the 2011 NFL lockout to a three-year deal worth $1.4 million.

[13] He also made the USA Today All-Joe Team for players who are talented and had put up good numbers, but did not receive a Pro Bowl bid.

[27] As a result of the Seahawks 13–3 regular season record, Baldwin and the rest of the team received a first-round bye.

[30] In Super Bowl XLVIII against the Denver Broncos, Baldwin led all Seahawks wide receivers with five receptions for 66 yards and a touchdown in the 43–8 victory.

For all y'all who called us, the receiving corps, average, pedestrian, appetizers—I'm not going to say any names, but he knows who he is—I respect what you did on the field, but stick to playing football, because your analytical skills ain't up to par yet.

[38] In the season opener against the Green Bay Packers on Thursday Night Football, Baldwin had three receptions for 14 yards in the 36–16 victory.

[39] Baldwin had his second career regular-season 100-yard game in Week 7 against the St. Louis Rams, reeling in seven passes for 123 yards and a touchdown in a 28–26 defeat.

[40] In Week 14, Baldwin had five catches for 97 yards and a touchdown, and also drew a long pass interference penalty, in a 24–14 victory over the Philadelphia Eagles.

[43] In the Divisional Round against the Carolina Panthers, Baldwin caught a 16-yard touchdown pass for the first score of the game in an eventual 31–17 victory.

[46] Baldwin celebrated the touchdown with a vulgar pantomime which gained significant attention on social media as the "poopdown", and which earned a 15-yard penalty for unsportsmanlike conduct.

Baldwin later apologized for the incident, clarifying that the gesture was directed at opposing star cornerback Darrelle Revis, and that "it was just kind of a built-up frustration I was letting out in that sequence, between him and I.

[55] After his performance against the Browns, Baldwin joined Hall of Famer Jerry Rice as the only players in league history with at least 10 receiving touchdowns in a four-game span.

Baldwin also caught at least two touchdowns in four straight games, a feat that only Calvin Johnson and Hall of Famer Cris Carter have accomplished since 1960.

[60] The Seahawks' season ended the following week against the eventual NFC Champion Carolina Panthers in the Divisional Round.

[63] Baldwin started the 2016 season with a nine-catch, 92-yard outing against the Miami Dolphins, including a three-yard touchdown catch with less than a minute left to secure a narrow 12–10 victory for the Seahawks.

[64] Two weeks later against the San Francisco 49ers, Baldwin hauled in eight receptions for then a career-high 164 receiving yards, including a touchdown.

[65] In Week 10 on the road against the New England Patriots, he caught six passes for 59 yards, including three touchdowns, equaling a career-high.

[70] In the Divisional Round, Baldwin again had another strong performance against the second-seeded Atlanta Falcons, catching five passes for 80 yards and a touchdown.

[71] On January 23, 2017, Baldwin was named to his first career Pro Bowl as an injury replacement for Larry Fitzgerald of the Arizona Cardinals.

He also talks to other NFL players, most of whom are fellow Seahawks (such as Russell Wilson and Sidney Rice) or Stanford alumni (such as Andrew Luck, Richard Sherman, and Coby Fleener).

On November 17, 2013, Baldwin carried the flag of the Philippines onto CenturyLink Field to honor Typhoon Haiyan victims.

[92] Since retiring from the NFL in 2019, Baldwin has joined the board of Valor Worldwide, a Seattle digital media startup and publisher of the Internet property OurMilitary.com Archived November 6, 2019, at the Wayback Machine, which provides resources and services to the military community.

[96] In addition, Washington State Governor Jay Inslee appointed Baldwin to serve a four-year term on the state's Clemency and Pardons Board, which is tasked with reviewing particular criminal cases and providing recommendations to Inslee regarding the potential parole status of eligible inmates.

[97] In September 2021, Baldwin became CEO of Ventrk, a company focused on creating software aimed at empowering better decisions and improved results for stronger and healthier lifestyles.