This paper reports on a study that sought to improve pre-service science teachers' performance in the International Union of Pure and Applied Chemistry (IUPAC) nomenclature of aliphatic hydrocarbons using flipped classroom instructional approach (FCA). The study employed a single group pre- and post-test action research design. The sample size consisted of forty-five (45) 1st year pre-service science teachers of Foso College of Education (FOSCO) taking the Introduction to Organic Chemistry I course. Apurposive sampling technique of the non-probability sampling procedure was used to select the pre-service science teachers in an intact class. Pre-Service Science Teachers' Hydrocarbon Concept Diagnostic Test and Pre-Service Science Teachers' Hydrocarbon Concept Achievement Test were the research instruments used to collect the data. The instruments were pilot-tested at St. Ambrose College of Education and the reliability index found to be 0.75 for the pre-intervention test and 0.78 for the post-intervention test. After 9 weeks of engaging pre-service science teachers through in-class face-to-face activities and out-of-class online interaction of teaching and learning IUPAC nomenclature of aliphatic hydrocarbons, it came to light that pre-service science teachers' performance had improved greatly after they have been exposed to FCA as an intervention strategy. It was recommended that College of Education chemistry tutors should adopt newly interactive and innovative instructional strategies such as the FCA so as to help pre-service science teachers overcome challenging chemical concepts like the IUPAC nomenclature and other difficult chemistry concepts in and out of colleges or schools.