Recent research suggests that handwriting comprises two separate sub-skills, legibility and fluency. It remains unclear, however, how these sub-skills differ in their relationship to other abilities associated with handwriting including spelling, graphomotor skills, and selective attention. In this study, we sought to examine the extent and nature of concurrent relationships that may exist among these skills. Children in Years 3 (n = 293), 4 (n = 291), and 5 (n = 283) completed a large, group-administered battery to assess each of the above skills. Using multigroup SEM, we found that spelling, graphomotor skills, and selective attention together explained a moderate amount of variance in handwriting legibility (R2=.37–.42) and fluency (R2=.41–.58) and that these sub-skills differed in their concurrent relations. Graphomotor skills accounted for a relatively greater proportion of variance in legibility than did spelling. Conversely, there were relatively stronger contributions from variations in spelling ability to variations in fluency than from graphomotor skills. Furthermore, selective attention predicted handwriting fluency only, and it partially mediated the influence of graphomotor skills. This study further demonstrates that handwriting legibility and fluency are separable and complex skills, each differentially related to spelling, motor, and attentional abilities even in later primary school years.