This study examined how pre-service English teachers would utilize ChatGPT in three different English writing genres and perceive their writing competences. Participants were pre-service English teachers in the Department of English Education in Seoul, Korea. They initially wrote essays in cause and effect, comparison, and argumentative genres. They then received ChatGPT-generated feedback. To assess their perception in writing competences, macroscopic aspects (Thesis Statement, Idea Generation, Idea Development, and Idea Organization) and microscopic aspects (Topic Sentence, Coherence, Lexical Diversity, and Syntactic Complexity) were measured using a 5-point Likert scale. Responses collected before and after ChatGPT feedback were analyzed using Multivariate Analysis of Variance (MANOVA). Findings indicated that ChatGPT use led to perceived improvements in both macroscopic and microscopic aspects regardless of genre, while no significant differences were found between genres. This study highlights the potential of using ChatGPT to enhance English writing skills. It provides insights for AI-integrated writing education.