<p>Research consistently show that autistic youth are less physically active compared to their neurotypical peers. However, there is limited understanding of how gender influences physical activity (PA) patterns among neurodiverse youth compared to the general population. This study aims to examine 24-hour movement behaviors - PA, sedentary behavior (SB), and sleep duration - among autistic youth (<i>n</i> = 71) in Norway, in comparison to peers with Attention-Deficit/Hyperactivity Disorder (ADHD) (<i>n</i> = 411) and the general youth population (<i>n</i> = 3805). The data is from the Young-HUNT4 study, linked with diagnostic information from the Norwegian Patient Registry. Variables explored are objective accelerometer-measured PA, SB, and sleep duration, self-reported participation in organized and unorganized physical activities, and screen activities. Results confirms that autistic youth engage in lower levels of moderate-to-vigorous PA, while demonstrating similar levels of light PA. They also spend more time sitting and comparable time sleeping. Autistic youth participate less in sport and were less likely to use commercial gyms. However, their participation in outdoor activities were similar to their peers. Regarding screen activities, autistic youth spent more time playing video games, while youth with ADHD were more engaged in social media. Among autistic youth, the only gender difference found was in video games. In conclusion, autistic youth are less physically active overall and spend significant time in SB. However, their comparable participation in light PA suggests opportunities for promoting further participation. Additionally, exergaming could offer a promising avenue to increase PA in this population.</p>