Background: Platelets play an essential role in both coagulation system and the host immune defenses against infection including community-acquired pneumonia (CAP). This work aimed to study the possibility of using platelet count as an additional criterion to predict the outcome of hospitalized patients with CAP. Results: This prospective cohort study included 250 patients hospitalized with CAP. According to platelet count at admission, 15 (6%) patients showed thrombocytopenia (group I) and 202 (80.8%) showed normal platelet count (group II), while 33 (13.2%) patients showed thrombocytosis (group III). CAP patients with thrombocytosis had more significant respiratory complications including lung abscess (p = 0.02), empyema (p < 0.001), and pleural effusion (p = 0.01). Severe sepsis and septic shock were significantly encountered among CAP patients with thrombocytopenia (p = 0.02 and 0.03, respectively). CAP patients with thrombocytopenia significantly needed mechanical ventilation either invasive (p = 0.017) or even non-invasive (p = 0.047). Both CAP patients with thrombocytopenia or thrombocytosis had significant 30 days readmission (p = 0.034) and significant 30 days mortality (p = 0.016) when compared to CAP patients with normal platelet count. Both thrombocytopenia (p = 0.012) and thrombocytosis (p = 0.029) were independent predictors of 30 days mortality among hospitalized patients with CAP. Conclusions: Both thrombocytosis and thrombocytopenia are linked to adverse outcomes among hospitalized patients with CAP.