Purpose: The aim of this research paper is to significantly contribute to empirical research on the impact of sustainable supply chain management (SSCM) practices on sustainable performances of firms, with the moderating effect of process innovation (PI), in the manufacturing sector in Pakistan. This paper also theorizes comprehensive SSCM practices and sustainable performance models of firms and evaluates them empirically. Two aspects of SSCM experiences have been integrated into the model: internal management and external management practices of a firm's sustainability impact assessment. Research methodology: Using the data from 297 manufacturing firms in Pakistan, this research paper analyzes the influence of sustainable supply chain management practices on sustainable performances of firms with the moderation of process innovation in the said relationship. In this study, we used partial least-squares structural equation modelling (PLS-SEM) for data analysis. Results: The findings demonstrate that both internal management and external management SSCM practices have a positive and significant impact on a firm's sustainable performance, thus supporting hypotheses (H1-H4). Moreover, process innovation as a moderator has a statistically significant relationship between hypotheses H5 and H5c. Originality: For Pakistani firms, comprehensive performance models of SSCM practices are proposed and empirically evaluated. The results of this study help to support the hypotheses that internal and external SSCM practices are necessary for the service sector. Process innovation plays an important role if managed and implemented properly. A number of internal and external SSCM approaches and implications are recommended, along with firm size as a moderator.Sustainability 2020, 12, 2303 19 of 24 may investigate dynamic changes at various SSCM stages by using time series data or panel data. Reducing the subjective factors and biases of the participants and conducting a broader sample survey will be a future piece of work. This study used process innovation as a moderator. Future studies may incorporate other moderating variables, such as firm size, to test the relationship between SSCM practices and a firm's sustainable performance in the service sector of developing economies. Author Contributions: Conceptualization, R.W. and Y.S.; methodology, R.W.; software, H.M.S.; validation, R.W. and Y.S.; formal analysis, F.W.; investigation, R.W.; data curation, M.J.H.; writing-original draft preparation, H.K. and R.W.; writing-review and editing, R.W.; supervision, Y.S. All authors have read and agreed to the published version of the manuscript.