Kansas City Chiefs
Gonzalez was ranked as one of the top tight ends in the 1997 NFL draft and was considered a top 15 selection. The Chiefs traded up from the 18th to the 13th selection with the Tennessee Oilers to draft Gonzalez.
Gonzalez began his career in the 1997 season. He finished his rookie season with 33 receptions, two touchdowns, and a blocked punt on special teams, helping the Chiefs to finish with the best record in the American Football Conference (AFC). He was named to the NFL All-Rookie Team for the 1997 season. In the 1998 season, Gonzalez saw dramatic improvements with 59 receptions for 621 yards, and he also caught two touchdown passes for the second (consecutive) year.
The 1999 season saw Gonzalez again improving when he caught 76 passes for 849 yards and a career-high 11 touchdown receptions, earning his first Pro Bowl selection. In addition, he was named as a First Team All-Pro. In week 14 of the 2000 season, he had 11 receptions for 147 yards and a touchdown in a loss to the New England Patriots. In the 2000 season, he had 93 receptions for 1,203 receiving yards and nine receiving touchdowns. He was named to the Pro Bowl and as a First Team All-Pro for the 2000 season. In the 2001 season, he had 73 receptions for 917 receiving yards and six receiving touchdowns while earning his third career First Team All-Pro honor and Pro Bowl nomination. On November 4, against the San Diego Chargers, he threw his first professional pass, which went for 40 yards.
During the 2002 offseason, Gonzalez briefly resumed his basketball career, playing for the Miami Heat in the NBA Summer League. He appeared in two games, with his best outing being an 11 rebound performance in a 72–71 win against the Indiana Pacers. Despite never considering bringing Gonzalez to training camp due to his ongoing football career, then coach Pat Riley later stated that "If he ever would have pursued it, I think he would have been a 10-year pro".
In week 4 of the 2002 season, Gonzalez had seven receptions for 140 yards and a career-high three touchdowns in a win over the Miami Dolphins. In the 2002 season, he had 63 receptions for 773 receiving yards and seven receiving touchdowns to go along with yet another Pro Bowl nod. From 2003 to 2006, Gonzalez was the most productive tight end in the NFL. In the 2003 season, he had 71 receptions for 916 receiving yards and ten receiving touchdowns. For the fourth time in his career, he was named as a First Team All-Pro. He was named to his fifth consecutive Pro Bowl for the 2003 season. His best season statistically came in 2004, when he caught an NFL-record (for a tight end) 102 passes for 1,258 yards and seven touchdowns. In week 17, he had a career-high 14 receptions for 144 yards against the San Diego Chargers. He earned a spot in the Pro Bowl for his historic season. Gonzalez's single-season record of 102 receptions by a tight end stood for 8 years, until it was broken by Jason Witten during the 2012 season. In the 2005 season, he had 78 receptions for 905 receiving yards and two receiving touchdowns in another Pro Bowl season.
Starting late in 2006, Gonzalez began to close in on numerous team and league receiving records. He finished with 73 receptions for 900 receiving yards and five receiving touchdowns and earned his eighth consecutive Pro Bowl nomination. In 2006, Gonzalez broke wide receiver Otis Taylor's Chiefs team receiving yards and touchdowns mark, and also passed running back Priest Holmes for the team yards from scrimmage record.
In 2007, Gonzalez continued his productivity in spite of the generally poor play of the Chiefs' offense. Though the Chiefs finished at or near the bottom in most major offensive categories, Gonzalez led the Chiefs and all NFL tight ends in receptions (99) and receiving yards (1,172) while being named to his ninth straight Pro Bowl.
On October 14, 2007, Gonzalez broke the career touchdown reception record for tight ends previously held by Shannon Sharpe, as well as passing Ozzie Newsome for second in career receiving yards for a tight end. On December 23, 2007, Gonzalez recorded his third season with 1,000 receiving yards, tying him with Kellen Winslow, Todd Christensen, and Shannon Sharpe for most ever by a tight end, and on December 30, 2007, Gonzalez passed Shannon Sharpe for most receptions all time by a tight end.
In week 4 of the 2008 season, Gonzalez became NFL all-time leader in receiving yards for a tight end with 10,064, surpassing Shannon Sharpe. He recorded 96 receptions for 1,058 yards and was also elected to his tenth career Pro Bowl. For the fifth time in his career, he earned First Team All-Pro honors. Running up to the NFL trade deadline, the Packers and the Eagles were in last minute talks with the Chiefs to trade a third-round draft pick for him. But Chiefs' GM Carl Peterson said he wanted a second-round draft pick instead and the deal fell through.
During the 2009 offseason, Gonzalez again approached Chiefs management about a possible trade. Unlike the previous Chiefs management, new Chiefs' GM Scott Pioli told Gonzalez he would see what he could do.