Recent research suggests that handwriting comprises two separate subskills: legibility and fluency. It remains unclear, however, how these subskills differ in their relationship to other abilities associated with handwriting, including spelling, graphomotor, and selective attention skills. In this study, we sought to examine the extent and nature of concurrent relationships that may exist among these skills. Children in Year 3 (n = 293), Year 4 (n = 291), and Year 5 (n = 283) completed a large, group-administered battery to assess each of the above skills. Using multigroup structural equation modeling, we found that spelling, graphomotor, and selective attention skills together explained a moderate amount of variance in handwriting legibility (R2 = .37–.42) and fluency (R2 = .41–.58) and that these subskills 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, graphomotor, and attentional abilities even during later primary school years.