Software development presents various challenges for developers: Programming, problem-solving and communication skills are required in multiple deadline-oriented projects running in parallel. These challenges can adversely affect developers’ mental well-being and productivity. So far, software developers’ well-being has mainly been examined via questionnaires or extensive and costly setups in laboratory settings. Objective, continuous and minimally invasive measurements with wearables in real-life settings are scarce and remain underutilized. This exploratory study uses a mixed-method approach to investigate the cognitive load component of developer experience and how it impacts professional SAP software developers in their everyday working context. Previous studies have demonstrated that physiological activity recorded by wearables can effectively measure cognitive load. In this study, thirty professional SAP software developers evaluated their developer experience in a questionnaire. Twenty of them additionally recorded physiological data during one working day using the Empatica E4 wristband. During the recording, they documented their working tasks and rated their experienced cognitive load during those tasks. The questionnaire data served as support for the physiological data recording. Key findings are that subjective cognitive load ratings positively correlate with electrodermal activity and skin temperature, and negatively with wrist acceleration. Three task categories (development-heavy, collaboration-heavy and other) could be discriminated based on subjective load ratings. Skin temperature and wrist acceleration differed significantly between development-heavy and other tasks. Subjective evaluations of the software developers in this study indicate that work environment factors which the individual software developer cannot influence negatively impact the developer experience. This study motivates the use of wearables in a firm context to enable a holistic evaluation of developer experience by combining subjective and objective measures in a real-world setting. Efficient task scheduling and detecting first signs of burnout could be enabled, which increases the software developer’s well-being and productivity and long-term reduces sick days and turnover rates in firms.