A group of organizations forms an interorganizational collaborative to pursue a shared mission and tackle enormous challenges and issues that cannot be solved by individual organizations. Although some scholars tried to examine the relationship between driving factors, such as antecedents or key processes, with the performance level of interorganizational collaboratives, little consensus was found on the dimensions of organizational performance at the network level in the nonprofit literature. Therefore, this study aimed to better understand the dimensions of effective performance outcomes of interorganizational collaboratives. The target population for this study was a group of people with extensive experience with interorganizational humanitarian networks, and the locations of the sample groups from different international humanitarian interorganizational networks were in Switzerland and UK. The data consisted of nine exploratory semi-structured interviews with the participants to address the study's purpose, and this study employed a qualitative research methodology and critical incident interview technique. This study yielded a total of 27 critical incidents. In-depth thematic analysis using both deductive and inductive data analysis approaches was conducted. The findings of this study corroborated three well-established dimensions of organizational performance (i.e., knowledge, financial, and mission performance), conceptualized by a priori theoretical frameworks on organizational performance theories, which included the learning organization performance theory (McHargue, 2003; Watkins & Marsick, 1993, 1997, 1996) and strategic nonprofit performance framework (Kaplan, 2001). Additionally, a fourth and new network-level performance dimension, relational performance, was inductively derived from participants' understanding and experiences about organizational performance outcomes pertaining to the relational aspect of interorganizational collaboration in the humanitarian sector. The addition of the fourth dimension is a significant contribution to the human resource and organization development literature. This study has exemplified the efficacy of a qualitative research approach using Flanagan's (1954) CIT method to examine organizational performance at the network level. Also, practical implications on how to make an interorganizational collaboration more effective concerning the four organizational performance dimensions at the network level are presented. The results of the study could aid leaders and managers serving in an interorganizational collaborative in deepening their understanding of critical organizational performance dimensions at the network level.