Introduction: Chronic tension-type headache (CTTH) is a major health problem, although the previous data is very limited, especially in Indonesia. Cognitive disorders often occur in CTTH patients. In addition, stress factors (mental or physical), anxiety, depression, temperamental instability, that is, bigger emotional status are factors that can cause CTTH. Serotonin is involved in various behavioral functions, especially in the regulation of mood, aggressiveness and impulsiveness. Aim: To analyze the relationship between serotonin serum level with cognitive function on CTTH. Methods: This was a cross sectional study in the outpatient of neurological clinic dr. Kariadi Hospital Semarang between April - September 2019. The data consist ofserotonin levels, MoCA-Ina questionnaire, Hamilton Depression Rating scale (HDRS) score and Score Hamilton Anxiety Rating scale (HAM-A). Statistical analysis with fisher’s exact. Results: The data were obtained from 38 subjects which consisted of female (78.9%) and male (21.1%). There was a significant relationship between anxiety and cognitive function in CTTH. There was no significant relationship between depression and cognitive function on CTTH. Impaired cognitive function in CTTH is related to memory (90%) and executive domains (70%) in most cases. Discussion: There was no significant difference between normal and abnormal serum serotonin levels with impaired cognitive function. There was a significant association between low serum serotonin levels and anxiety in CTTH patients. There was no association between low serum serotonin levels and depression in CTTH patients. CTTH patients experienced cognitive impairments regarding memory and executive domains in most cases. Keywords: Chronic tension type headache, cognitive, MoCA-Ina, serotonin