The Kingdom of Saudi Arabia is one of the countries in the Middle East burdened with type 2 diabetes (T2D). This type of diabetes is associated with an increase in the body's resistance to insulin action. Elevated blood pressure is one of the most important diseases that accompany T2D. Many experimental and clinical studies have shown the effectiveness of olive leaves extract (OLEx) in controlling T2D, as well as hypertension. This review aimed to collect clinical studies conducted in humans that prove the effectiveness of OLEx or its active constituent (oleuropein) in combating T2D, hypertension, and hypolipidemia. Several studies conducted in humans (diseased and healthy) showed the effectiveness of OLEx or oleuropein in reducing both blood glucose and lipids. It also improved the vascular functions and reduced inflammation associated with high blood pressure and diabetes. The mechanisms behind these pharmacological activities were to scavenge free radicals, increase insulin production, and reduce its resistance, raise nitric oxide synthesis, and dilate blood vessels. From toxicological studies in experimental animals, it has been shown that the OLEx may be safe to use. In conclusion, studies on humans showed the effectiveness of OLEx in managing T2D, hyperlipidemia, and hypertension, but there were limited-number trials and did not use large numbers of participants, and therefore large studies must be conducted to document effectiveness and safety of OLEx.