Background <p>Although ordering food online has become a leading lifestyle factor among the Chinese urban population, its health impact is understudied. This study aims to examine this aspect, focusing on online takeaway food impacts related to foodborne illness, nutrition, and suboptimal health (i.e., an intermediate status between being healthy and diagnosed with a disease) on consumers.</p> Methods <p>A snowball sampling method was adopted, targeting urban consumers aged 18–59 across mainland China by posing an e-questionnaire survey. Information collected includes demographic data, foodborne illness occurrence, nutrition and suboptimal health impacts when ordering online takeaway foods. The questionnaire was adapted from the Diet Quality Questionnaire and Sub-Health Measurement Scale version 1.0. Descriptive statistical methods, Mann‒Whitney test, and Spearman’s correlation test were employed to analyse the data.</p> Results <p>A total of 610 questionnaires were included. Consumers ordering online takeaway foods at least once per week (hereon termed as ‘frequent consumers’) often experienced fake reviews (50.71%), hygiene issues (54.03%) and foodborne illness (58.29% reporting lower gastrointestinal symptoms). Frequent consumers had lower diet quality, with higher Global Dietary Recommendation (GDR)-Limit scores (Mann-Whitney, <i>p</i> = 0.0011), lower GDR-Healthy (<i>p</i> = 0.0033) and overall GDR scores (<i>p</i> &lt; 0.0001) than infrequent consumers. Additionally, the frequency of online takeaway food consumption was negatively associated with overall GDR scores (<i>p</i> = 0.0392). After adjusting for demographic characteristics, physical subhealth scores were lower among frequent consumers (<i>p</i> = 0.0157), with differences in GDR-Limit (<i>p</i> = 0.0087), GDR-Healthy (<i>p</i> = 0.0221) and overall GDR scores (<i>p</i> &lt; 0.0001) remaining; after further adjusting for lifestyle factors, the differences in GDR-Healthy and overall GDR scores persisted. While the differences in the aforementioned scores were not significant within the medical subgroup after adjustment.</p> Conclusions <p>This study suggests that online takeaway food consumption in urban China is a significant lifestyle, posing a risk of foodborne illness and associating with poorer diet quality and physical health status to a certain extent. Monitoring of food safety and fake review in food delivery should be strengthened, along with public education on nutrition. Further clinical research should evaluate the association between online takeaway food consumption and health risks.</p>