Using collaborative action research, this study aimed to investigate the practice of implementing an aesthetic thematic curriculum in a preschool in Taiwan. The author served as a curriculum consultant and co-teacher with two early childhood teachers in a mixed-age preschool class. The participants were 22 young children aged 3 to 5. Data sources included classroom observations, interviews, teaching reflection notes, aesthetic ability assessment, and other documentation. The major findings are as follows. (1) Based on young children’s life experiences, the co-teachers applied a thematic approach to integrating the aesthetic domain and other learning domains in the aesthetic thematic curriculum, focusing on the topic of “Beautiful Restaurants.” (2) The young children’s aesthetic abilities were developed in terms of exploring and perceiving, performing and creating, and responding and appreciating. Moreover, there was a significant difference in the children’s aesthetic abilities. (3) The co-teachers promoted their professional development in aesthetic curriculum design and aesthetic teaching skills. Recommendations for early childhood aesthetic education and teacher education are discussed.