Introduction: nutritional support (NS) leads complica- tions that must be detected and prompt treated. Objective: to estimate the incidence of some complica- tions of nutritional support in critically ill patients. Materials and methods: a multicenter, descriptive, prospective study in patients with NS in intensive care units. Studied variables included medical diagnosis, nutritional status, length of NS, path, type of formula and ten complications. Results: 419 patients evaluated, 380 received enteral nutrition (EN) and 39 parenteral nutrition (PN). The high gastric residue was the most incident complication in the ENS (24.2%), followed by diarrhea (14%) and with- drawal tube (6.6%). The high gastric residue and diar- rhea were associated with the duration of the NS (p < 0.05). For the PNS the complication most incidents were hypophosphatemia (38.5%), followed by catheter sepsis (15.4%). The duration of the NS was associated with cholestasis, sepsis and hypophosphatemia (p < 0.05). Conclusions: complications of highest incidence were the high gastric residue for EN and hypophosphatemia for the PN; the withdrawal of the tube is a complication that claims further monitoring. The duration of the NS was the variable that showed greater association with the complications studied. Is a must to get consensus on com- plications definitions for comparisons establishment and best international standards target, furthermore propose protocols in order to decrease complications incidence of NS to fulfill the critical ill patient requirements.