An Algerian international, Slimani made his international debut in 2012 and played at the Africa Cup of Nations in 2013, 2015 and 2017, and was part of the Algeria side that won the 2019 tournament. He was also part of Algeria's squad at the 2014 FIFA World Cup, where he finished as the team's joint top scorer with two goals. As of March 2021, he has won over 70 international caps and scored 31 goals, making him Algeria's second highest all-time goalscorer.