This qualitative study examined how participating in-service teachers demonstrated linguistically and culturally responsive mathematical teaching (LCRMT) competences after they completed a year-long National Professional Development Program grant-funded project. A two-dimensional LCRMT framework was developed to measure participating teachers' mathematical and mathematics-related competences. The qualitative data source was from three in-service teachers' observations and interviews. The interview and observation data were analyzed using open and axial coding and activity systems. Three themes emerged: 1) mathematics-related content teaching practices, 2) tools to support mathematics learning, and 3) teachers' mindsets and attitudes towards English Learner (EL) teaching. The researchers then compared verbatim examples using activity systems to examine the following research question: How did participating urban in-service teachers apply linguistically and culturally responsive mathematics teaching competences for ELs learned at a university EL teacher training program to their actual mathematics teaching in the classroom? The results, in general, indicated that the urban in-service teachers demonstrated improvement of LCRMT strategies that they used in their actual mathematics teaching after they completed the university training. However, challenges in the areas of mathematical discourse competences and teachers' sociocultural beliefs toward ELs revealed the need for ongoing professional support.