Background and objectives: Outdoor workers are at increased risk of developing non-melanoma skin cancer. We aimed to address the lack of validated German-language measurement instruments for outdoor workers’ sun safety behavior and knowledge by compiling and validating two questionnaires. Participants and methods: By expert consensus, items for the assessment of protective behavior (OccuSun) were compiled based on existing instruments. For knowledge, a translation of the Skin Cancer and Sun Knowledge (SCSK) scale was selected. After a pre-test, a validation study including 68 outdoor workers (62% female) was conducted in 2020. Results: The retest reliability was r = 0.93 (95% confidence interval: 0.86–0.96) for the protection score and r_s = 0.78 (0.67–0.86) for the knowledge score. Protective behaviors were correlated with respective diary data (0.38 ≤ r_s ≤ 0.74, p < 0.001) and skin pigmentation changes (–0.23 ≥ r_s ≥ –0.42, 0.007 ≤ p ≤ 0.165) but not with self-reported sunburn frequency (0.21 ≥ r_s ≥ –0.04). Conclusions: Among German outdoor workers, two questionnaires for the assessment of sun protection behavior (OccuSun) and knowledge (SCSK) demonstrated good reliability. The OccuSun had generally good validity. Both instruments are fit for subsequent validation to determine their sensitivity to change.