In the present contribution, the effects of different types of mass‐transfer on homogeneous catalytic reactions are addressed. In particular, emphasis is given to the effects of mass‐transfer on the precatalytic reactions as well as the turnover frequency. Various types of transport effects are considered. These include gas–liquid and liquid–liquid mass transfer, segregation and mixing of solutions, as well as dissolution kinetics of sparingly soluble organometallics and cage effects. A number of criteria are suggested for comparing the rates of mass transfer with various rates of reaction. A checklist is proposed for the experimentalist to assist in identifying potential mass‐transfer control issues. Simple steps to mitigate these complications are suggested.