Quality of life (QoL) impacts the future health outcomes of people with Autism Spectrum Disorders (ASD). Past research, although limited, has shown that people with ASD often experience a lower quality of life. Yet, there's not much research focusing on the quality of life of young adults with autism, especially in Saudi Arabia, where it appears no studies have assessed the QoL of adults with autism. This study aims to evaluate and compare the quality of life between young adults with ASD and those without (a control group) in Saudi Arabia to pinpoint areas that could be improved. The study included 439 participants, with 107 being adults with autism and 332 without (a 1:3 ratio). An Arabic translation of the World Health Organization (WHO) QoL short version (WHOQOL-BREF) was used for assessment. The average age of participants with ASD was 24.82 years, with the average age for diagnosis and starting treatment being around 7.4 and 8.28 years, respectively. Those with ASD reported a significantly lower quality of life (1.68) in all areas compared to the control group (3.96), especially in social relationships (average score=27.01). A negative correlation was found between the age at diagnosis and at starting treatment with overall QoL, suggesting that a delay in diagnosis is associated with a lower quality of life. The study reveals that adults with ASD in Saudi Arabia have a lower QoL in all areas compared to the general population, indicating that early diagnosis and intervention could improve their quality of life. These results emphasize the need for policy changes to better support individuals with ASD in improving their quality of life.