Knowledge required to teach mathematics at the university level is a current and relevant research topic in Mathematics Education. Thus, the case study presented in this article pertains to one mathematics lecturer whose knowledge is examined focusing on his delivery of a Multivariable Calculus course. The data required were gathered via classroom observations and a semi-structured interview and were subsequently analyzed through the lens of the Mathematics Teacher's Specialized Knowledge model. The interactions among different components of the lecturer's specialized knowledge that were identified in terms of intra-domain and inter-domain relationships provide empirical support for the complex and integrated nature of the mathematics lecturer's knowledge.