Language learners today have access to a much wider choice of resources and language-support tools that aid their writing processes. While research on the convenience and flexibility of the writing resources that learners use in real-life writing activities have argued for a re-conceptualization of writing ability, little is known about the effect of using them in a writing assessment setting. Accordingly, the present study aimed to examine whether L2 learners’ use of writing resources in a writing test might have an effect on their writing performance. Furthermore, we also investigated how the effects of the writing resources might vary by test takers’ writing proficiency and scoring domains. Results showed that the group who had access to writing resources outperformed the group who were not given the online resource, but both groups’ scores were within the same scoring descriptor. The significant score improvement was more evident in the low- and intermediate-level learners. In a questionnaire, test takers reported that they normally use the writing resources in real-life writing situations and also found the online resource features helpful in improving their writing performance and agreed upon introducing such features in future writing tests.