The writing section of the SAT, based on but not directly comparable to the old SAT II subject test in writing, includes multiple choice questions and a brief essay. The essay subscore contributes about 28% towards the total writing score, with the multiple choice questions contributing 70%. This section was implemented in March 2005 following complaints from colleges about the lack of uniform examples of a student's writing ability.

The multiple choice questions include error identification questions, sentence improvement questions, and paragraph improvement questions. Error identification and sentence improvement questions test the student's knowledge of grammar, presenting an awkward or grammatically incorrect sentence; in the error identification section, the student must locate the word producing the source of the error or indicate that the sentence has no error, while the sentence improvement section requires the student to select an acceptable fix to the awkward sentence. The paragraph improvement questions test the student's understanding of logical organization of ideas, presenting a poorly written student essay and asking a series of questions as to what changes might be made to best improve it.

The essay section, which is always administered as the first section of the test, is 25 minutes long. All essays must be in response to a given prompt. The prompts are broad and often philosophical and are designed to be accessible to students regardless of their educational and social backgrounds. For instance, test takers may be asked to expound on such ideas as their opinion on the value of work in human life or whether technological change also carries negative consequences to those who benefit from it. No particular essay structure is required, and the College Board accepts examples "taken from [the student's] reading, studies, experience, or observations." Two trained readers assign each essay a score between 1 and 6, where a score of 0 is reserved for essays that are blank, off-topic, non-English, not written with a Number 2 pencil, or considered illegible after several attempts at reading. The scores are summed to produce a final score from 2 to 12 (or 0). If the two readers' scores differ by more than one point, then a senior third reader decides. The average time each reader/grader spends on each essay is less than 3 minutes.