Differentiated instruction (DI) is a teaching practice implemented in multi-ability classrooms to meet the diverse learning needs of all students. National polices such as The Disability Discrimination Act and Disability Standards for Education, together with state policies such as Queensland's P-12 Curriculum Assessment and Reporting Framework, encourage teachers to foster a classroom environment that is supported through DI-led teaching and learning practices. Due to the scarcity of research conducted in Australian secondary schools, this research study will explore how early career teachers use DI in their multi-ability classrooms. A qualitative study was conducted with six early career teachers from a secondary state school situated on the Gold Coast, Queensland. Individual semi-structured interviews were used to ask participants about their use of DI in their classrooms. Data were analysed using thematic analysis which uncovered two major themes: differentiated instruction from a preservice teacher perspective and differentiated instruction from an early career teacher perspective. Findings revealed that teachers followed the curriculum-related elements of Tomlinson's model of differentiation when using DI, both as pre-service and in-service teachers. The teachers discussed the impact of this teaching strategy on their learners' engagement, achievement, and self-efficacy, and acknowledged the teacher colleagues and school leaders in the school environment who supported them to adopt this comprehensive instructional pedagogy. However, teachers were not convinced that their teacher education courses had prepared them well enough to use DI during their professional experience placements, and they were confused between the terms "differentiated instruction" and "reasonable adjustments". Teachers discussed class sizes, inadequate planning time and duration of lessons, learner behaviour, lack of resources and professional development, and skill weakness as barriers that hindered their effective implementation of DI in their classrooms. Further research into the experiences of early career teachers and their use of this teaching pedagogy is needed to ensure that they are adequately prepared and supported to overcome possible challenges, to rectify misconceptions, and to effectively utilise DI to support and enhance the learning of all students in their classrooms.