Objective. To explore associations of serum neurofilament light chain (sNfL) at admission with clinical deficits and the long-term prognosis of acute ischaemic stroke (AIS). Methods. We recruited 110 AIS patients with serum sampled at hospital arrival. The concentrations of sNfL were detected by a Simoa HD-1 analyser. We first investigated the determinants of sNfL levels at admission within the study population. Associations of sNfL levels with National Institutes of Health Stroke Scale (NIHSS) scores and modified Rankin Scale (mRS) scores were then tested. We further divided the patients into revascularized and nonrevascularized groups, and the associations of sNfL levels with NIHSS and mRS scores were assessed in these subgroups. Results. Age, sex, stroke history, and the time between the onset of illness and arrival at the hospital were independent influencing factors of sNfL levels within the study population. The sNfL levels at admission were correlated with the NIHSS scores 7 days after stroke (
p
=
0.004
) across all subjects but showed no correlation with the NIHSS scores at admission (
p
=
0.293
) or the mRS scores 6 months after stroke (
p
=
0.065
). Further analysis revealed that in the nonrevascularized group of AIS patients, the sNfL levels at admission were positively correlated with NIHSS scores (NIHSS at admission,
p
=
0.005
; NIHSS 7 days after stroke,
p
=
0.003
) and negatively correlated with mRS scores (
p
=
0.011
). Conclusion. sNfL levels at admission could be a potential biomarker for predicting clinical deficits and prognosis in the natural course of AIS.