Amyotrophic lateral sclerosis (ALS) is a relentless, progressive, and presently incurable neurodegenerative disease. Its drug development has been hampered by the lack of effective biomarkers for early diagnosis, progression and prognosis. Recently, significant progress has been made for the identification of body fluid biomarkers for ALS, which conferred both theoretical and practical feasibility for the early diagnosis and progression monitoring. Meanwhile, it also facilitated identification of genes and/or pathways for the pathogenesis of ALS. This review summarized biomarkers identified from cerebrospinal fluid, blood and urine of ALS patients and their clinical implications.