2014 Bontempelli made his senior debut in the 's 38 point loss to in round 5 of the
2014 AFL season. when he was injured with an
adductor strain. In 2015 he picked up a career-high 28 disposals while playing , also kicking 2 goals, taking 7 marks and collecting 7 tackles. Bontempelli collected 24 disposals, 3 marks, 2 behinds and 7 tackles in the ' seven point elimination final loss to . He was named as one of their best on ground. Bontempelli came third in the
Charles Sutton Medal, the award for the
Best and fairest player for the Western Bulldogs. He was only topped by
Easton Wood and
Bob Murphy in the count. On top of this, he more than tripled his
Brownlow Medal votes from last season, leading the club for total Brownlow votes that season after picking up thirteen votes at just the age of 19. Six of those votes were in the first two rounds after back-to-back best on ground performances, while he collected two other best on ground performances in round 15 and round 22. He was once again named in the 22 Under 22 team as a midfielder. He signed a long-term contract with the Bulldogs in September, keeping him at the club until 2019.
2016–2017: Premiership success 2016 Bontempelli had his best year yet in 2016, playing every single game of the season, including the fairytale premiership win. Bontempelli was elevated into the club's leadership group at the beginning of the year. Bontempelli collected a career-high 33 disposals in the Bulldogs' round 8 match against . During the 2015 and 2016 period, he was often used during ruck contests, getting at least one hitout in 40 out of his 47 games during this period. On 5 June 2016, in the absence of acting captain
Easton Wood, who was filling in for injured regular captain
Robert Murphy, Bontempelli captained the Western Bulldogs against at
Etihad Stadium, becoming the youngest match day captain in the AFL since
Jack Trengove in 2012. He was instrumental in the Bulldogs' four consecutive finals, including the
2016 AFL Grand Final, which was the club's first premiership victory in 62 years. His season was rewarded with the
Charles Sutton Medal, finishing 71 votes clear of second-placed
Dale Morris. He also won the John Schultz Community Award. He had five games in which he was voted best on ground, and finished 8th overall in the voting. Bontempelli made the 22 under 22 team for the third year in a row, named the captain of the team. He also made the
All-Australian team for the first time, named on the interchange bench, alongside veteran teammate
Matthew Boyd.
2017 Bontempelli missed the
2017 JLT Community Series after a minor ankle injury at the club's pre-season camp in January. He had season-best games against Carlton in round 2 and Sydney in round 17, kicking 2 goals and collecting 30 disposals in each game. He led the team in total number of behinds, tackles, inside 50s, clearances, contested marks and contested possessions by the end of the season. Former and great
Gerald Healy described Bontempelli as someone who 'could end his career as the greatest player in the history of the Western Bulldogs', after his 23 disposal, 2 goal performance against in round 20. After another great season for the Bulldogs, Bontempelli claimed his second
Charles Sutton Medal, and was once again named as captain of the 22 under 22 team, his fourth consecutive year being named in the team and second consecutive year as captain. On 20 November 2017, Bontempelli was named vice-captain of the club for the
2018 AFL season, following Murphy's retirement and Wood's elevation to captain from vice-captain. Bontempelli had a similar vote count to his previous year in the
2017 Brownlow Medal, with a total of 19 votes, including 6 best on ground games in rounds 2, 6, 7, 14, 17 and 20. He finished in 7th.
2018–2019: Vice-captaincy 2018 Bontempelli played all but one game in the
2018 AFL season, in a disappointing season for the Bulldogs where they missed finals for the second year in a row. On 10 July 2018, Bontempelli was taken to hospital with severe appendicitis and had surgery to resolve the issue. Bontempelli was then placed on the sidelines in order to allow him to recover from the surgery, and subsequently missed round 7. This meant he missed what was due to be his 100th game. However, he ended up playing his 100th AFL game in the 's 44 point loss to in round 19, where he collected 22 disposals. Bontempelli broke his career high record for disposals twice in two consecutive matches in rounds 21 and 22, against and respectively. Bontempelli came 3rd in the
Charles Sutton Medal count, behind
Lachie Hunter and
Jack Macrae. For the fifth consecutive year, Bontempelli was named in the 22 under 22 team, setting the record as the first player to be named in the 22 under 22 team for 5 consecutive years. He only polled 9 votes in the
2018 Brownlow Medal, his lowest count since his debut year. Bontempelli signed a three-year contract extension with the Bulldogs in November, after which he stated "I've made no secret about the love I have for the Club, and how I want to play a key role in the future success of this playing group,". After questions as to why he only signed a shorter deal than expected, Bontempelli said "There's a bit of intrinsic value for me to continue to stay accountable to what I want to achieve. As an individual player I think I've got a lot of growth ahead of me and it keeps me invested from day to day."
2019 Bontempelli had another successful year in
2019, taking the Bulldogs to the finals series as the team's vice-captain. Bontempelli had 5 games where he collected 30 or more disposals. His 27 disposal, 3 goal performance in round 7 against the future premiers, , was one of his best for the season. A high bump from Bontempelli on defender
Nick Haynes in the penultimate round of the season resulted in Haynes getting a fractured larynx and Bontempelli narrowly missing suspension. Bontempelli was heavily tagged in the Bulldogs' elimination final loss to , resulting in a loss for the Bulldogs, adding to the growing rivalry of the two clubs. Bontempelli made the All-Australian squad for the second time in his career. He was named on the wing, as there was fierce competition for the highly contested midfield spots. Bontempelli also won the
AFL Coaches Association Player of the Year award, winning with a total of 107 votes, 17 votes ahead of second placed
Patrick Dangerfield. He was the first player to win the award since it was first introduced in 2003, with 312 game Bulldog player
Bob Murphy describing him as a "generational player". Bontempelli won the
Charles Sutton Medal for the 3rd time, gathering 299 votes, giving him a margin of 29 votes against the second placed
Josh Dunkley. In December 2019,
Easton Wood stood down as Western Bulldogs captain, and Bontempelli was announced as the new captain from 2020. Bontempelli tied with fellow Bulldog
Jack Macrae to collect 22 votes in the
2019 Brownlow Medal, judged best on field in 5 games—rounds 1, 3, 15, 19 and 20.
2020–present: Captaincy in the 2020
Bushfire Relief Match 2020 Prior to the
2020 home-and-away season, he was selected to represent Victoria in the
State of Origin for Bushfire Relief Match, played in February 2020. He played with teammate
Jack Macrae and against fellow Bulldog
Jason Johannisen. In the match, he kicked 2 goals. In the main 2020 AFL season, Bontempelli had a stand-out game against in round 12, where he had 33 disposals, 2 goals and 12 clearances. Bontempelli was again recognised for his impressive performance throughout the season, and was named in the
All-Australian team for the third time in his career, and the second year in a row, this time as a forward. His selection on the forward line caused backlash as Bontempelli, primarily a midfielder, took the spot of forward that "could have gone to players that primarily play in the forward line". Bontempelli captained the Bulldogs to the
2020 finals series in a relatively fruitful year, playing every single game. Bontempelli came runner-up in the
Charles Sutton Medal voting, losing to defender
Caleb Daniel by a mere 10 votes. He also won the club's Scott West Most Courageous Player Award. placing him at 22nd overall in the count.
2021 After a mediocre opening round to the
2021 AFL season, Bontempelli lifted his performance dramatically and had a best-on-ground performance the following week, kicking the winning goal to seal the win against . Bontempelli played his 150th AFL career game in round 5, where the strongly defeated . He was named as the game's best on ground by most media sources, after his 33 disposals and 3 goals helped the Bulldogs win their fifth game in a row, seeing the Bulldogs go undefeated for 5 rounds for the first time since 1946. Bontempelli again led his team to victory in round 8 of the season, where his 32 disposals, 10 clearances, 8 tackles and 1 goal saw him heralded as the team's best on ground for the game. Bontempelli equalled his highest goal tally for a game after kicking 4 goals in the team's 111-point victory over in round 10, again being named as best on ground. It was announced that Bontempelli had signed a four-year contract with the Bulldogs on 25 May 2021, where he stated that it was "an exciting time" for the Bulldogs and himself as a part of the team. By the end of Round 10, Bontempelli was tipped to be the favourite for the
2021 Brownlow Medal, leading AFL.com.au's Brownlow predictor with 17 votes. He ultimately finished runner-up with 33 votes to Port Adelaide's
Ollie Wines. Bontempelli won the Charles Sutton Medal for the fourth time.
2022 Dealing with injury and fluctuating team performance, Bontempelli had a more grounded year, missing selection in the All-Australian team for the first season since 2018. A switch into the forward line in round 5 and called the best player of the year by sports journalist
Mark Robinson.
2024 Bontempelli played every game of the
2024 on the way to his third
Leigh Matthews Trophy, sixth All-Australian team and sixth Charles Sutton Medal. He was also named as the All-Australian Captain for the first time. After controversially finishing second in the Brownlow Medal the previous season, there was again controversy as he only polled 19 votes to finish 13th. With decisions such as not awarding any votes for his Round 2 performance against , where he had polled all 10 AFL Coaches Association points, coming under scrutiny, amid renewed calls for umpires to be allowed access to statistics before they vote. He would eventually lead the Dogs to the Finals, where they would lose to in the Elimination Final.
2025 Bontempelli suffered a complex calf injury in the opening minutes of a preseason practice match, and missed the first five rounds of the
2025 AFL season. He returned in round 6 to play a pivotal role in the Bulldogs' win over St Kilda, kicking two goals from 30 disposals. ==Personal life==