Effects of urban decay on office rental values have not been researched in South African cities. The purpose of this study is to test if urban decay is still evident and has a negative effect on rental values of office buildings in the Johannesburg Central Business District (CBD). In conducting this research, a questionnaire was distributed to 48 office building managers within the Johannesburg CBD. The results obtained show that the majority of building managers agree to the fact that urban decay is still evident in the Johannesburg CBD and has a negative effect on office rental values. Respondents were of the opinion that factors such as abandoned buildings and high crime rates were features of urban decay which contribute negatively to office rentals in the Johannesburg CBD. This urban decay factors were more prominent or allocated same weightage for instance than factors such as market condition, interest rates and rental property demand. This research paper highlights the economic consequences of urban decay on commercial properties.