This study aimed to develop near-infrared spectroscopy (NIRS) calibrations for nitrogen (N) and carbon (C) contents of sugarcane (Saccharum spp.) leaves. The performances of two portable (LabSpec5000 and Phazir1018) and one laboratory (XDS) spectrometers were compared using samples collected from field trials with three sample preparation states (green, dried, dried crushed sugarcane leaves). The LabSpec5000 spectrometer appeared to be more appropriate for in-field applications, showing better calibration characteristics than the Phazir1018 for both N and C content determination. The best calibrations were those based on spectra obtained from the laboratory-based instrument (XDS) using dried crushed samples. This improved performance is probably due to the instrument characteristics and to the sample homogeneity (dried crushed leaves exclusively). This study demonstrated that it is possible to assess the N and C status of sugarcane by direct foliar diagnosis with NIRS. Foliar diagnosis based on NIRS offers cheaper, faster and easier alternative to traditional chemistry methods. It provides opportunities to monitor the nutrient status in-field with possible links to applications associated with precision agriculture (PA) or improved research and development (R&D) methodologies. NIRS also offers analytical possibilities in sugarcane cropping areas where no laboratories are available.