This study determined the effects of workplace deviance on employees' job performance in selected Research Institutes in Oyo State, Nigeria. A multistage random sampling technique was used to sample two hundred and fifty five (255) respondents. Data were collected through a structured questionnaire and were analyzed using descriptive and inferential statistical tools. Results revealed that mean age of respondents was 36.9 years and that majority (53.7%) of the respondents were male. The hierarchical regression analyses results indicated that overall job performance was significantly related to political deviance (b1 = -2.015, p < 0.05), personal deviance (b1 = -2.531, p < 0.05) and production deviance (b1 = 1.734, p < 0.05) This study concluded that despite various forms of workplace deviance identified in the study area, employees still perform better in their respective job assigned to them but not up to the maximum level expected. Finally, the study recommended that measure should be put in place to tame this act in other to achieve organizational goals. It was however recommended that conducive work environment be put in place to reduce work deviant behaviors. So also, training and workshops for the employees, both local and international level that can enhance their performance should also be put in place to reduce work place deviance.