Abstract The objective of this study was to determine the genetic parameters and variance components of the economically important fleece traits staple fineness (SF), staple length (SL), fiber diameter (FD) and fiber length (FL) in yearling Inner Mongolia Cashmere goats (IMWC). Data collected in 2008–2011 from 5 Arbas Cashmere goat flocks were analyzed. Fixed effects were determined using a generalized linear model with least square means. Variance components and genetic parameters were determined using the restricted maximum likelihood method. By ignoring or including maternal additive genetic effects and maternal permanent environment effects, and considering whether direct additive genetic and maternal additive genetic effects were correlated or not, six different single-trait animal models were obtained. A log likelihood ratio test was conducted to choose the most appropriate model. Then, genetic correlations among fleece traits were obtained using the average information restricted maximum likelihood method with multi-trait models. Year of production and herd had highly significant influences on all fleece traits (P 0.05). The log likelihood ratio test indicated that neither maternal additive genetic effects nor maternal permanent environment effects had a significant influence on the traits examined in this study. Direct additive heritabilities ( h d 2 ) were 0.27, 0.28, 0.34 and 0.17 for SF, SL, FD and FL, respectively, which is moderate to low. Direct additive genetic correlations were negative (−0.40) between SL and SF, but were positive (0.45) between SF and FD. Genetic correlations among the other traits were low, ranging from −0.17 to 0.12. The purpose of this study was to determine the genetics parameters of fleece traits to help improve the genetics of the Inner Mongolia Cashmere goats (IMWC).