Urban fireﬁghters are at risk of posttraumatic stress disorder (PTSD) because of their occupational exposure to trauma event. PTSD has been recognized as public health problem because it links to many health consequences including cardiovascular disease. This study was conducted in 2 phases. The first phase; a cross-sectional study, was aimed to determine a prevalence of risk of PTSD among all Bangkok firefighters and to access its associated factors. The second phase; a longitudinal study, aimed to access an association between risk of PTSD and changes of cardiovascular biomarker (Brain Natriuretic Peptide (BNP), Troponin T (TnT), and high-sensitive C-reactive protein (hs-CRP)) after 6-months follow-up. In the first phase of the study, all Bangkok firefighters were recruited for self-reported questionnaire. 302 of 1215 firefighters (24.90%) were met the suggested PCL cut-point criteria for civilian (PCL Scores ≥ 30). Health problems, smoking status, alcohol consumption, physical activity, sleep quality, duration of work, and past exposure to major fire in Thailand were associated with risk of PTSD (p-value<0.05). In phase 2, all firefighters from 2 purposively selected firefighter stations were recruited to participate. Blood check-up was performed in August, 2017 and February, 2018. 19 risk of PTSD and 35 non-risk of PTSD firefighters were participated. Brain-derived neurotrophic factor (BDNF), which is a member of the neurotrophin family of growth factors reflected for long-term memory, was investigated as a biomarker of PTSD. At baseline of study, the results showed a significant different BDNF concentration between risk of PTSD and non-risk of PTSD firefighters. Two cardiovascular biomarkers (hs-CRP and BNP) were associated with PTSD. After 6 month follow-up, 27.8% of firefighters were loss to follow-up and 14 of them were excluded because of blood samples. 12 risk of PTSD and 13 non-risk of PTSD firefighters were completed follow-up. General characteristic of remained firefighters was not different from baseline (p-value>0.05). The results showed that only BNP was associated with risk of PTSD (adjusted OR=31.22). In conclusion, firefighter at risk of PTSD was increased risk of cardiovascular biomarker change. Further intervention and policy related to coping mental health among firefighter should be introduced for reducing the risk of cardiovascular disease.