Spelling and handwriting are related skills which are critical for writing but are typically assessed separately. Doing so makes it more difficult to understand their respective development. We describe the creation and evaluation of a tool for their concurrent assessment: the Spelling and Handwriting Legibility Test (SaHLT). We examined whether (a) sentence spelling and handwriting legibility could be reliable and valid, independent measures of English spelling and handwriting legibility and (b) whether spelling and handwriting legibility can be measured concurrently. A total of 1461 primary-aged children (Mage = 9.14 years-old, SD = 12.80) completed the SaHLT and background tests. The SaHLT was a sensitive, reliable, and valid measure of spelling and handwriting. Multi-group factor analyses revealed the test to be a robust concurrent measure. The SaHLT offers a cost and time saving method of measuring two key skills of writing. This is important for assessments in practice and for furthering our understanding of the relationship between spelling and handwriting.