The search for efficient and versatile reaction medium to perform transition-metal-catalyzed reactions is a continuous challenge to the synthetic community. Organic solvents have been traditionally employed for this task, nevertheless, new environmentally friendly, safe, and economically viable alternatives are still highly sought after. In this context, herein, we present an overview of some interesting applications of aqueous microemulsions (oil-in-water, O/W) for transition metal catalyzed reactions as an alternative and promising aqueous-organic reaction medium that has been found to be a highly effective tool in overcoming some environmental or practical issues presented by traditional organic solvents.