Continuous incidence of governance failures, fraud, corruption and inefficiencies necessitate increasing demand for public sector performance. Nigerian government is insensitive to the plight of the citizens to effectively generate and optimize the usage of available resources. All efforts established to delineate the actions and standards of behaviours of civil servants such as good leadership styles, code of conduct and integrity seem not to be in existence and these consequently affect the performance of the public sector. This study therefore, examined standards of behaviour and public sector performance. The study employed the two popular survey research instruments (questionnaire and interview) to collect data concurrently, analyse separately and merge results during interpretations. The target population for quantitative analysis is One Thousand and Fifty (1,050), Six (6) from each of the 175 MDAs in Nigeria as at December, 2018. Krejcie Morgan sample size determination was used in arriving at the 280 samples used in gathering quantitative data, ten (10) participants were purposively selected for the interviews. Descriptive and inferential statistics were used in analysing the data; hypotheses were tested with Partial Least Square Structural Equation Modelling (PLS-SEM). Outcome indicated significant positive relationship between leadership quality, code of conduct and public sector performance, integrity is not significant. The conclusion from the study is that leadership styles in public sector influence performance and also adherence with the code of conduct. The study therefore recommends that Nigerian government should strengthen leadership styles in all MDAs and agencies saddled with code of conduct responsibilities be further strengthened to ensure efficient public service delivery in the Nigerian public sector entities.