Urban trees are increasingly experiencing drought stress due to more frequent and severe drought periods. This stress leads to reduced growth, structural damage and even mortality, further exacerbating feedback effects within the urban hydrological cycle. Currently, tree health assessments by arborists rely primarily on visual inspections, which often detect stress symptoms too late for effective intervention. To address this issue, early drought stress detection methods are essential. This review examines existing methods for detecting drought stress in urban trees, evaluating their scalability, market availability and usability for practitioners. We conducted a two-part literature analysis: (1) a systematic review of stress detection methods applied to urban trees between 2010 and 2024, and (2) a snowball search assessing the potential and limitations of the individual methods found in the systematic review. The systematic review revealed that in urban areas, Acer, Quercus and Tilia are the most commonly investigated tree taxa. The most common methods are leaf gas exchange measurements, analysis of plant water potentials and chlorophyll fluorescence. Compared to studies in non-urban areas, soil moisture monitoring is less common in urban tree studies. The snowball search showed that urban tree drought stress monitoring is in its nascent stage. Of all identified methods, only soil moisture sensors and microtensiometers were deemed easy to use and commercially available, yet both lack scalability for city-wide application. Furthermore, there remains a significant gap between fine-scale, tree-based assessments and broad-scale monitoring approaches. Bridging this gap with integrated monitoring strategies will be crucial for improving early drought stress detection and urban tree management.