Dietary counselling and oral nutritional supplements (ONS) are recommended for managing malnutrition. A recent systematic review demonstrated (in separate analyses) that dietary counselling and dietary counselling with ONS improved energy intake, weight and some indices of body composition, although there was considerable heterogeneity. The present analysis aimed to examine the effects on mortality and nutritional indices of dietary counselling given with or without ONS and to explore the heterogeneity in the meta-analyses aiming to characterise the groups most likely to benefit from these interventions. A systematic review and meta-analysis was performed using Cochrane methodology. Twenty-six studies were included in the analysis: 12 comparing dietary counselling with usual care and 14 comparing dietary counselling and ONS if required with usual care (2123 participants). Quality of studies varied. Dietary counselling given with or without ONS had no effect on mortality [relative risk (fixed) = 1.12; 95% confidence interval = 0.86-1.46] but was associated with significant but heterogeneous benefits to weight [mean difference (random) = 1.7 kg; 95% confidence interval = 0.86-2.55], energy intake and some aspects of body composition. Subgroup analyses taking into account clinical background, age, nutritional status, type and length of intervention failed to reveal any differences in mortality, weight change and energy intake between groups. There were insufficient data on functional outcomes to explore these findings. Dietary counselling given with or without ONS is effective at increasing nutritional intake and weight but adequately-powered studies in similar patient populations and standardised for factors that might account for variations in response are required.