Growing studies have revealed associations between smartphone addiction, depression and anxiety. However, most studies failed to examine the complex symptom-level connection, limiting insights into how specific smartphone addiction symptoms interact with mental health outcomes. This study aims to identify central and bridge symptoms within the smartphone addiction-depression-anxiety network among Chinese university students. A nationwide sample of 99,941 Chinese university students completed the Smartphone Addiction Scale for College Students (SAS-C), the Center for Epidemiologic Studies Depression Scale (CES-D), and the Generalized Anxiety Disorder Scale (GAD-7). Network analysis was employed to estimate symptom connections, centrality, and bridge symptoms. Withdrawal behavior (SA1), depressed mood (D3), everything is an effort (D4), nervous (A1), and uncontrollable worry (A2) emerged as central symptoms. Excessive app use (SA5), D10 (could not get going), D4 (everything is an effort), and A1 (nervous) served as critical bridge symptoms linking smartphone addiction with depression and anxiety. This study reveals the complex interactions between smartphone addiction and depression and anxiety symptoms in university students. Targeted interventions addressing everything an effort, nervous, withdrawal behavior, and excessive app use may disrupt the comorbidity cycle.