Mannose-binding lectin (MBL) serum levels or genetic polymorphisms are known to be associated with autoimmune diseases. We investigated MBL2 genetic polymorphisms in 95 patients with ankylosing spondylitis (AS) and in 252 healthy controls. MBL2 promoter polymorphisms at -550 (H/L), -221 (Y/X), +4 (P/Q), and exon polymorphisms at codon 52 (Arg/Cys), 54 (Gly/Asp, or A/B), and 57 (Gly/Glu) were investigated using polymerase chain reaction and restriction fragment length polymorphism. Genetic polymorphisms were analyzed using SPSS (ver 12.0) and Haploview (ver 4.2). MBL2 single-nucleotide polymorphisms (SNPs) were not significantly different between patients with AS and controls. By haplotype analysis, LYPB frequency was significantly lower in AS (10.7% vs. 21.3%, OR 0.441, 95% CI: 0.266-0.733, P value = 0.001, Pc value = 0.008). The frequency of LYPA (15.4% vs. 9.2%, OR 1.802, 95% CI: 1.097-2.961, P value = 0.019, Pc value = 0.101) and HYPB (3.5% vs. 0.8%, OR 4.457, 95% CI: 1.289-15.409, P value = 0.011, Pc value = 0.060) tended to be higher in AS. Clinical characteristics of AS were not associated with any MBL2 SNP or haplotype. In summary, haplotypes of MBL2 genetic polymorphisms were found to be associated with AS, which suggests that MBL2 genetic polymorphisms may play a role during the development of AS.