Graduate students will go on to be future scholars in sustainability, and the ability to design and execute research projects are necessary skills for them to build scholarship. In response, many STEM programs, including construction engineering, civil engineering, and architectural engineering, provide graduate level courses in research design and methods. Graduate students learn the skills in research methodology either formally from such a course or informally from their advisor(s). However, little to no evidence has been obtained to quantify such learning outcomes. This paper reports a case study that was designed to assess graduate students' understanding and implementation of research methodologies. To do so, a mixed research methods approach was conducted. The work applies mixed research methods. Data were collected from the Michael Horman Sustainability Symposium, a forum for faculty and students from multiple U.S. universities focusing on the discussion of sustainability topics. The attendees (N = 53) were required to prepare a statement to detail their research plan and associated research method and to present in a focus group setting. The authors evaluated the statement in the topic (i.e., merit, impacts, originality, and relevance) and methodology (i.e., rationale, feasibility, creativity, and scalability) using a 5-point Likert scale. The evaluation criteria are based on ASCE journal reviewing standards. Both quantitative analysis on the evaluation scores and qualitative analysis on the focus group notes were performed. Results reveal that graduate students know how to identify emerging research problems in sustainability, yet lack the capability to select appropriate research methods to support the intended investigation. The findings help better understand the research methodologies required for conducting sustainability studies, and illuminate teaching strategies that can strengthen students' capability of problem-solving.