Objective: Social media (SM) have flourished and are affecting human lives on an unprecedented scale. Problematic social media use (PSMU) is a recently emerging problematic behavior that affects both physical and mental health. The purpose of this study was to investigate whether problematic users of SM display attentional bias (AB) toward SM-related cues, as well as the relationships between AB, the severity of PSMU, and negative emotions. Method: 1000 college students were recruited through classes and online forums and then tested using the Bergen Social Media Addiction Scale (BSMAS). Eventually, 60 participants, identified by the cut-off point for BSMAS, consented to participate in the study and were divided into two groups (i.e., a problematic use group and a typical use group). The severity of PSMU and negative emotions (i.e., anxiety, depression, social fear, and loneliness) were evaluated by self-report questionnaires. AB was assessed by an addiction Stroop task and a dot-probe task (DPT). Results: PSMU was found to be positively associated with anxiety (r = 0.28, p < 0.05), depression (r = 0.35, p < 0.01), and social fear (r = 0.38, p < 0.01), but not with loneliness (r = 0.19, p = 0.15). Participants with a tendency toward PSMU displayed AB toward SM-related cues in the DPT [F (1, 58) = 26.77, p < 0.001, ηp2 = 0.32], but not in the Stroop task [F (1, 58) = 0.61, p = 0.44, ηp2 = 0.01]. Moreover, AB toward SM-related stimuli was found to be positively correlated with the severity of PSMU (r = −0.51, p < 0.001), anxiety (r = −0.37, p < 0.01), depression (r = −0.51, p < 0.001), and social fear (r = −0.30, p < 0.05) in the DPT. Conclusions: Problematic users of SM show AB towards SM-related cues in the DPT, which is more reliable for assessing AB than the Stroop task. Moreover, it is suggested that in clinical interventions we should work to change the AB towards SM-related stimuli and improve negative emotions to decrease risks of PSMU.