Hello Shivani,

Yes, Improvement mark sheet is accepted by Delhi University for admission in undergraduate courses. But keep in mind while applying that if you are using your improved score to enter best of four calculation then you have to take all the scores from the improvement mark sheet only. If you've applied for improvement in less than 5 subjects then the remaining scores will be entered from the previous mark sheet.

Hope this answers your query, feel free to ask for more info.