Context: Software security engineering provides the means to define, implement and verify security in software products. Software security engineering is performed by following a software security development life cycle model or a security capability maturity model. However, agile software development methods and processes, dominant in the software industry, are viewed to be in conflict with these security practices and the security requirements. Objective: Empirically verify the use and impact of software security engineering activities in the context of agile software development, as practiced by software developer professionals. Method: A survey (N=61) was performed among software practitioners in Finland regarding their use of 40 common security engineering practices and their perceived security impact, in conjunction with the use of 16 agile software development items and activities. Results: The use of agile items and activities had a measurable effect on the selection of security engineering practices. Perceived impact of the security practices was lower than the rate of use would imply: This was taken to indicate a selection bias, caused by e.g. developers’ awareness of only certain security engineering practices, or by difficulties in applying the security engineering practices into an iterative software development workflow. Security practices deemed to have most impact were proactive and took place in the early phases of software development. Conclusion: Systematic use of agile practices conformed, and was observed to take place in conjunction with the use of security practices. Security activities were most common in the requirement and implementation phases. In general, the activities taking place early in the life cycle were also considered most impactful. A discrepancy between the level of use and the perceived security impact of many security activities was observed. This prompts research and methodological development for better integration of security engineering activities into software development processes, methods, and tools.