There is little understanding of physical activity (PA) and sedentary behavior as preventive health behaviors in autistic adults. Technology has been used as an educational and social intervention tool for autistic individuals, yet it is also associated with low PA and high sedentary time (ST) in the neurotypical population. This study aimed to examine the prevalence of self-reported PA and ST and their relationships with various technology uses in autistic adults. We employed a Qualtrics online survey that consisted of the International Physical Activity Questionnaire-Short Form, Sedentary Behavior Questionnaire, and National Alliance for Mental Illness's digital technology use survey. 229 responses (74.6% under 35 years of age; 64.1% males) satisfied the response validity criteria and were included in the analyses. The majority of participants (78%) met the recommended PA amount of [greater than or equal to] 600 metabolic equivalent of task (MET)-minutes/week (median, 1,812 total MET-minutes/week), but they were also overly sedentary on both weekdays (median, 8 h/day) and weekends (median, 7 h/day). Stepwise multiple regression analyses revealed that variance of ST in weekday (45%) and weekend (43%) was largely explained by quality of life ([beta] = -0.31; [beta] = -0.33) and technology use time ([beta] = 0.31; [beta] = 0.26) (all p < 0.01). While technology can be an effective tool to support social and academic abilities in autistic adults, the use of technology devices needs to be monitored with care as it may put these individuals at risk for sedentary lifestyles and associated chronic diseases.