This study aims to describe the characteristics of performance assessment variables, leadership style, OCB, and employee engagement, and analyze their influence on each other at KPP Pratama Malang Selatan. Specifically, this study examines the influence of performance assessment on employee engagement, leadership style on employee engagement, employee engagement on OCB, and the relationship between performance assessment and leadership style on OCB both directly and through employee engagement. This study is explanatory with data collection using a survey. The population of the study was 91 employees, but the sample used was 80 State Civil Apparatus (ASN) who did not carry out leadership functions at KPP Pratama Malang Selatan. The data were analyzed using path analysis with the help of the WarpPLS 6.0 program. The results of the study indicate that: (1) performance assessment has a significant effect on employee engagement; (2) leadership style has a significant effect on employee engagement; (3) employee engagement has a significant effect on OCB; (4) performance assessment has a significant effect on OCB; (5) leadership style has a significant effect on OCB; (6) performance assessment has a significant effect on OCB through employee engagement; (7) leadership style has a significant effect on OCB through employee engagement. Based on these findings, it is recommended that KPP Pratama Malang Selatan continue to improve performance assessment and leadership style to strengthen employee engagement and OCB.