Current technologies for the point-of-care diagnosis of traumatic brain injury (TBI) lack sensitivity, require specialist handling or involve complicated and costly procedures. Here, we report the development and testing of an optofluidic device for the rapid and label-free detection, via surface-enhanced Raman scattering (SERS), of picomolar concentrations of biomarkers for TBI in biofluids. The SERS-active substrate of the device consists of electrohydrodynamically fabricated submicrometre pillars covered with a plasmon-active nanometric gold layer, integrated in an optofluidic chip. We show that the device can detect N-acetylasparate in finger-prick blood samples from patients with TBI, and that the biomarker is released immediately from the central nervous system after TBI. The simplicity, sensitivity and robustness of SERS-integrated optofluidic technology might eventually help the triaging of TBI patients and assist clinical decision making at point-of-care settings.