Junior national teams Hendrickx has represented Belgium at junior level in both Under 18 and Under 21 age groups. In 2010, Hendrickx was a member of the Belgium Under-18 side at the
2010 Youth Olympic Games in
Singapore. The team won the bronze medal, defeating
Ghana 4–1 in the third-place playoff. He made his debut for the Belgium Under 21 side, in 2012 at a qualifying for the
Junior World Cup. Hendrickx was also a member of the team at the Junior World Cup in
New Delhi, India, where the team finished sixth.
Senior national team Hendrickx made his senior international debut for
Belgium in 2012, at the
Champions Trophy. He was a reserve player at the
2016 Summer Olympics, where Belgium won a silver medal. In November 2018, he was named in the squad for the
2018 World Cup in
Bhubaneswar, India. At the tournament, he finished as top scorer alongside
Blake Govers of Australia with 7 goals. At the
2019 EuroHockey Championship, he also was the top goalscorer together with three other players with five goals. On 25 May 2021, he was selected in the squad for the
2021 EuroHockey Championship. He was top goal scorer at Tokyo 2020 with 14 goals using the LTD X.
2020 Olympics Alex Hendrickx won Olympic Gold at
Tokyo 2020. He was the top goal scorer with 14 goals. He scored a hat-trick in the opening game in their 4–1 win against
The Netherlands. He scored another hat-trick against
South Africa. In the final group game against
Great Britain he suffered a bad injury when he got a stick to the face. He recovered for the knock out stages wearing a protective headband. ==Club career==