<p>The purpose of this study was to measure the effect of motivational interviewing on both reducing internet addiction and digital game addiction in adolescents. A parallel-group randomised controlled trial was adopted. The study population consisted of ninth-grade (14–15&#xa0;years of age) high school students in a city in Turkiye. The study was completed by 88 participants (experimental: 44; control: 44). The data were collected using a Personal Information Form, the Young Internet Addiction Test, and the Digital Game Addiction Scale. The experimental group received a preparatory session and five weekly motivational interviewing sessions. Instruments were administered to both groups before (pre-test) and after the intervention (post-test), and at follow-up tests 3 and 6&#xa0;months after the final session. The data were analysed using the two-way mixed design and the Bonferroni Comparison Test. The mean scores of internet addiction and digital game addiction decreased significantly after the motivational interviewing in the experimental group compared to the control group (<i>p</i> &lt; 0.001) in both the post-test and follow-up tests.</p><p> <i>Conclusion</i>: The present study concluded that motivational interviewing may be associated with reductions in mitigating symptoms of internet addiction and digital game addiction behaviours among adolescents. Motivational interviewing could be implemented to reduce internet addiction and digital game addiction behaviours.&#xa0;</p><p><i>Trial registration</i>: The study was registered on a clinical trial database (NCT06721702). The study started on December 11, 2023 (actual date on which the first participant was enrolled). <Table Float="No" ID="Taba"> <tgroup cols="2"> <colspec align="left" colname="c1" colnum="1" /> <colspec align="left" colname="c2" colnum="2" /> <tbody> <row> <entry nameend="c2" namest="c1"> <p><b>What is Known:</b></p> <p>• <i>Internet addiction and digital game addiction are two increasingly important problems among adolescents.</i></p> <p>• <i>Digital games and online activities negatively affect adolescents’ physical, social, and psychological health.</i></p> </entry> </row> <row> <entry nameend="c2" namest="c1"> <p><b>What is New:</b></p> <p>• <i>Motivational interviewing was an effective technique to reduce online gaming and internet addiction.</i></p> <p>• <i>A motivational interviewing program comprising at least six sessions could be implemented to promote behavioural change in adolescents.</i></p> </entry> </row> </tbody> </tgroup> </Table></p>