This study attempted to examine the Effects of Psychological Availability of an employee at work on Business Performance of Zanzibar Revenue Board in Tanzania. The study is based on data collected from 100 respondents constituting the working staff of Zanzibar Revenue Board sampled by non-probability method by convenient sampling technique. The data was collected by personal interviews and analyzed by descriptive statistics tools by excel. The findings show that, Psychological Availability of an employee at work has high effects on the business performance of Zanzibar Revenue Board. Based on the findings, the study recommends Zanzibar Revenue Board to employ various strategies to increase psychological availability of employees at work because it has a high effect on the business performance of the organization.