The prevalence of dengue has been alarming worldwide and most cases are found to reside in Asia. Brunei Darussalam is not excluded from dealing with the dengue spread within the country. There are four circulating serotypes of dengue which are DENV-1, DENV-2, DENV-3 and DENV-4. The predominant serotype in Brunei tends to vary from year to year and according to the research in Thailand, antibodies are responsible for the change of the predominant serotype. In this Chapter, the main focus of the study is to forecast the trend of dengue cases using time series analysis with a multiplicative model and to determine if there is a significant relationship, if any, between the number of dengue cases and both rainfall & average temperature in Brunei Darussalam, using multiple regression. The result shows that the predicted values of trend for the dengue fever cases are underestimates as well as overestimates. Furthermore, the result also shows that there is a significant relationship between the number of dengue cases and rainfall.