The German Commission for the Investigation of Health Hazards of Chemical Compounds in the Work Area has re‐evaluated the maximum concentration at the workplace (MAK value) of 5 ml/m3 for diethylamine, considering all toxicity endpoints. Available unpublished study reports and publications are described in detail. The critical effect of diethylamine is atrophy of the olfactory mucosa in rats and mice in a 2‐year study. Since 2014 the Commission uses an empirical approach to set MAK values for substances with critical effects on the upper respiratory tract or the eyes. A NOAEC for atrophy of the olfactory mucosa was not obtained in the 2‐year study. A benchmark concentration of 4 ml/m3 (BMDL05) as a substitute for a NOAEC is calculated from the data of the mouse, the most sensitive species. Therefore, the MAK value for diethylamine is lowered to 2 ml/m3. The chronic NOAEC for systemic toxicity is judged to be 16 ml/m3. As local effects are critical, the assignment to Peak Limitation Category I is confirmed. The excursion factor of 2 is set with a read‐across to cyclohexylamine. The momentary value is lowered to 5 ml/m3. Because there are no studies on developmental toxicity, the assignment to Pregnancy Risk Group D is confirmed as well. Diethylamine is not genotoxic and not carcinogenic. Skin contact may contribute significantly to systemic toxicity and diethylamine is designated with an “H” notation. Sensitization is not expected from the limited data.