Cardiovascular disease (CVD) is a worldwide healthcare burden. However, it is thought that CVD risk can be lowered by changing a number of modifiable risk factors such as diet, and this includes the intake of tea. This review assessed the effectiveness of green tea, black tea or black/green tea extracts in healthy adults and those at high risk of CVD. We found 11 randomised controlled trials, four of which examined black tea interventions and seven examined green tea interventions. There were variations in the dosage and form (drink, tablets or capsules) of the black and green tea interventions, and the duration of the interventions ranged from three months to six months. Adverse events were reported in five of the included trials. These included a diagnosis of prostate cancer, hospitalisation for influenza, appendicitis and retinal detachment; these are unlikely to be associated with the intervention. The results showed black and green tea to have a beneficial effect on lipid levels and blood pressure, but these results were based on only a small number of trials that were at risk of bias. Analysis conducted over both tea types showed beneficial effects of tea on LDL-cholesterol and blood pressure but again this was based on only a few trials that were at risk of bias. To date the small number of studies included suggest some benefits of green and black tea on blood pressure and lipid levels but more longer-term trials at low risk of bias are needed to confirm this.